diff --git a/src/api/common.ts b/src/api/common.ts
index 42b386b2a..ef097e8b1 100644
--- a/src/api/common.ts
+++ b/src/api/common.ts
@@ -424,6 +424,13 @@ export interface IExternalBaseLayer {
      *
      */
     options?: any;
+    /**
+     * An optional URL to a thumbnail image to display in the base layer switcher UI
+     *
+     * @type {string}
+     * @since 0.15
+     */
+    thumbnailImageUrl?: string;
 }
 
 
diff --git a/src/components/base-layer-switcher.tsx b/src/components/base-layer-switcher.tsx
index 5adab8c2a..a024f22c3 100644
--- a/src/components/base-layer-switcher.tsx
+++ b/src/components/base-layer-switcher.tsx
@@ -16,8 +16,24 @@ export interface IBaseLayerSwitcherProps {
 
 /**
  * The BaseLayerSwitcher component provides a user interface for switching the active external
- * base layer of the current map
- * @param props 
+ * base layer of the current map.
+ *
+ * When any base layer has a `thumbnailImageUrl` set, the switcher renders as a thumbnail grid
+ * instead of a radio-button list.
+ *
+ * @example
+ * ```tsx
+ * <BaseLayerSwitcher
+ *   locale="en"
+ *   externalBaseLayers={[
+ *     { name: "OpenStreetMap", kind: "OSM", thumbnailImageUrl: "https://example.com/osm.png" },
+ *     { name: "Satellite", kind: "BingMaps", thumbnailImageUrl: "https://example.com/sat.png" }
+ *   ]}
+ *   onBaseLayerChanged={(name) => console.log(name)}
+ * />
+ * ```
+ *
+ * @since 0.15
  */
 export const BaseLayerSwitcher = (props: IBaseLayerSwitcherProps) => {
     const { locale, externalBaseLayers } = props;
@@ -31,6 +47,57 @@ export const BaseLayerSwitcher = (props: IBaseLayerSwitcherProps) => {
     React.useEffect(() => {
         setSelected(visLayers.length == 1 ? visLayers[0].name : STR_EMPTY);
     }, [visLayers]);
+
+    const visualLayers = externalBaseLayers.filter(ebl => isVisualBaseLayer(ebl));
+    const hasThumbnails = visualLayers.some(layer => !!layer.thumbnailImageUrl);
+
+    if (hasThumbnails) {
+        const onThumbnailClick = (layerName: string) => {
+            setSelected(layerName);
+            props.onBaseLayerChanged?.(layerName);
+        };
+        const onThumbnailKeyDown = (e: React.KeyboardEvent, layerName: string) => {
+            if (e.key === "Enter" || e.key === " ") {
+                e.preventDefault();
+                onThumbnailClick(layerName);
+            }
+        };
+        const noneLabel = tr("NONE", locale);
+        return <div className="base-layer-switcher-thumbnail-container">
+            <div
+                role="button"
+                tabIndex={0}
+                aria-label={noneLabel}
+                aria-pressed={strIsNullOrEmpty(selected)}
+                className={`base-layer-switcher-thumbnail-item${strIsNullOrEmpty(selected) ? " base-layer-switcher-thumbnail-item-selected" : ""}`}
+                onClick={() => onThumbnailClick(STR_EMPTY)}
+                onKeyDown={(e) => onThumbnailKeyDown(e, STR_EMPTY)}
+            >
+                <div className="base-layer-switcher-thumbnail-none-placeholder">{noneLabel}</div>
+                <div className="base-layer-switcher-thumbnail-label">{noneLabel}</div>
+            </div>
+            {visualLayers.map(layer => {
+                const isSelected = layer.name === selected;
+                return <div
+                    key={`base-layer-thumb-${layer.name}`}
+                    role="button"
+                    tabIndex={0}
+                    aria-label={layer.name}
+                    aria-pressed={isSelected}
+                    className={`base-layer-switcher-thumbnail-item${isSelected ? " base-layer-switcher-thumbnail-item-selected" : ""}`}
+                    onClick={() => onThumbnailClick(layer.name)}
+                    onKeyDown={(e) => onThumbnailKeyDown(e, layer.name)}
+                >
+                    {layer.thumbnailImageUrl
+                        ? <img className="base-layer-switcher-thumbnail-image" src={layer.thumbnailImageUrl} alt="" />
+                        : <div className="base-layer-switcher-thumbnail-none-placeholder" aria-hidden="true">{layer.name}</div>
+                    }
+                    <div className="base-layer-switcher-thumbnail-label" aria-hidden="true">{layer.name}</div>
+                </div>;
+            })}
+        </div>;
+    }
+
     return <div>
         <div className="base-layer-switcher-item-container">
             <label className="bp3-control bp3-radio">
@@ -39,7 +106,7 @@ export const BaseLayerSwitcher = (props: IBaseLayerSwitcherProps) => {
                 {tr("NONE", locale)}
             </label>
         </div>
-        {externalBaseLayers.filter(ebl => isVisualBaseLayer(ebl)).map(layer => {
+        {visualLayers.map(layer => {
             return <div className="base-layer-switcher-item-container" key={`base-layer-${layer.name}`}>
                 <label className="bp3-control bp3-radio">
                     <input className="base-layer-switcher-option" type="radio" value={layer.name} checked={layer.name === selected} onChange={onBaseLayerChanged} />
diff --git a/src/styles/index.css b/src/styles/index.css
index 99622bb2d..71a4de4bb 100644
--- a/src/styles/index.css
+++ b/src/styles/index.css
@@ -19,6 +19,68 @@
     background-color: white;
 }
 
+/* Base Layer Switcher - Thumbnail grid mode */
+
+.base-layer-switcher-thumbnail-container {
+    display: flex;
+    flex-wrap: wrap;
+    gap: 6px;
+    padding: 4px;
+    max-width: 320px;
+}
+
+.base-layer-switcher-thumbnail-item {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    width: 74px;
+    cursor: pointer;
+    border: 2px solid transparent;
+    border-radius: 4px;
+    padding: 2px;
+    box-sizing: border-box;
+}
+
+.base-layer-switcher-thumbnail-item:hover {
+    border-color: #888;
+}
+
+.base-layer-switcher-thumbnail-item-selected {
+    border-color: #106ba3;
+}
+
+.base-layer-switcher-thumbnail-image {
+    width: 70px;
+    height: 50px;
+    object-fit: cover;
+    border-radius: 2px;
+    display: block;
+}
+
+.base-layer-switcher-thumbnail-none-placeholder {
+    width: 70px;
+    height: 50px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    background-color: #e8e8e8;
+    border-radius: 2px;
+    font-size: 11px;
+    color: #555;
+    text-align: center;
+    box-sizing: border-box;
+    padding: 2px;
+}
+
+.base-layer-switcher-thumbnail-label {
+    font-size: 11px;
+    text-align: center;
+    margin-top: 2px;
+    word-break: break-word;
+    max-width: 70px;
+    line-height: 1.2;
+}
+
 .iframe-iehack-zindex {
     position: absolute;
     border: none;
diff --git a/test/components/base-layer-switcher.spec.tsx b/test/components/base-layer-switcher.spec.tsx
index e6091526f..eb578feff 100644
--- a/test/components/base-layer-switcher.spec.tsx
+++ b/test/components/base-layer-switcher.spec.tsx
@@ -1,6 +1,6 @@
 import * as React from "react";
 import { describe, it, expect, vi } from "vitest";
-import { render } from "@testing-library/react";
+import { render, fireEvent } from "@testing-library/react";
 import { IExternalBaseLayer } from "../../src/api/common";
 import { BaseLayerSwitcher } from "../../src/components/base-layer-switcher";
 import { STR_EMPTY } from "../../src/utils/string";
@@ -53,4 +53,69 @@ describe("components/base-layer-switcher", () => {
         expect((radio[2] as HTMLInputElement).value).toBe("Stamen - Toner");
         expect((radio[2] as HTMLInputElement).checked).toBe(false);
     });
-});
\ No newline at end of file
+    it("Renders thumbnail grid when at least one layer has thumbnailImageUrl", () => {
+        const onBaseLayerChanged = vi.fn();
+        const layers: IExternalBaseLayer[] = [
+            { name: "OpenStreetMap", kind: "OSM", visible: true, thumbnailImageUrl: "https://example.com/osm.png" },
+            { name: "Stamen - Toner", kind: "Stamen", thumbnailImageUrl: "https://example.com/stamen.png" }
+        ];
+        const { container } = render(<BaseLayerSwitcher externalBaseLayers={layers} onBaseLayerChanged={onBaseLayerChanged} locale="en" />);
+        // Should render thumbnail container, not radio buttons
+        const thumbnailContainer = container.querySelectorAll(".base-layer-switcher-thumbnail-container");
+        expect(thumbnailContainer).toHaveLength(1);
+        const radio = container.querySelectorAll(".base-layer-switcher-option");
+        expect(radio).toHaveLength(0);
+        // NONE + 2 layers = 3 thumbnail items
+        const items = container.querySelectorAll(".base-layer-switcher-thumbnail-item");
+        expect(items).toHaveLength(3);
+        // The visible layer (OpenStreetMap) should be selected
+        const selectedItems = container.querySelectorAll(".base-layer-switcher-thumbnail-item-selected");
+        expect(selectedItems).toHaveLength(1);
+        // Should render thumbnail images
+        const imgs = container.querySelectorAll(".base-layer-switcher-thumbnail-image");
+        expect(imgs).toHaveLength(2);
+        expect((imgs[0] as HTMLImageElement).src).toContain("osm.png");
+        expect((imgs[1] as HTMLImageElement).src).toContain("stamen.png");
+    });
+    it("Renders thumbnail grid with NONE selected when multiple layers are visible", () => {
+        const onBaseLayerChanged = vi.fn();
+        const layers: IExternalBaseLayer[] = [
+            { name: "OpenStreetMap", kind: "OSM", visible: true, thumbnailImageUrl: "https://example.com/osm.png" },
+            { name: "Satellite", kind: "BingMaps", visible: true, thumbnailImageUrl: "https://example.com/sat.png" }
+        ];
+        const { container } = render(<BaseLayerSwitcher externalBaseLayers={layers} onBaseLayerChanged={onBaseLayerChanged} locale="en" />);
+        const items = container.querySelectorAll(".base-layer-switcher-thumbnail-item");
+        expect(items).toHaveLength(3);
+        // NONE item should be selected (first item)
+        expect(items[0].classList.contains("base-layer-switcher-thumbnail-item-selected")).toBe(true);
+        expect(items[1].classList.contains("base-layer-switcher-thumbnail-item-selected")).toBe(false);
+        expect(items[2].classList.contains("base-layer-switcher-thumbnail-item-selected")).toBe(false);
+    });
+    it("Calls onBaseLayerChanged when a thumbnail item is clicked", () => {
+        const onBaseLayerChanged = vi.fn();
+        const layers: IExternalBaseLayer[] = [
+            { name: "OpenStreetMap", kind: "OSM", thumbnailImageUrl: "https://example.com/osm.png" },
+            { name: "Satellite", kind: "BingMaps", thumbnailImageUrl: "https://example.com/sat.png" }
+        ];
+        const { container } = render(<BaseLayerSwitcher externalBaseLayers={layers} onBaseLayerChanged={onBaseLayerChanged} locale="en" />);
+        const items = container.querySelectorAll(".base-layer-switcher-thumbnail-item");
+        // Click the second item (OpenStreetMap)
+        fireEvent.click(items[1]);
+        expect(onBaseLayerChanged).toHaveBeenCalledWith("OpenStreetMap");
+    });
+    it("Renders placeholder for layers without thumbnailImageUrl in thumbnail mode", () => {
+        const onBaseLayerChanged = vi.fn();
+        const layers: IExternalBaseLayer[] = [
+            { name: "OpenStreetMap", kind: "OSM", thumbnailImageUrl: "https://example.com/osm.png" },
+            { name: "Stamen - Toner", kind: "Stamen" } // no thumbnail
+        ];
+        const { container } = render(<BaseLayerSwitcher externalBaseLayers={layers} onBaseLayerChanged={onBaseLayerChanged} locale="en" />);
+        const thumbnailContainer = container.querySelectorAll(".base-layer-switcher-thumbnail-container");
+        expect(thumbnailContainer).toHaveLength(1);
+        const imgs = container.querySelectorAll(".base-layer-switcher-thumbnail-image");
+        expect(imgs).toHaveLength(1); // only the layer with a URL gets an img
+        const placeholders = container.querySelectorAll(".base-layer-switcher-thumbnail-none-placeholder");
+        // NONE item placeholder + "Stamen - Toner" placeholder
+        expect(placeholders).toHaveLength(2);
+    });
+});
diff --git a/viewer/generic.html b/viewer/generic.html
index d6b47a21e..713d8a5cf 100644
--- a/viewer/generic.html
+++ b/viewer/generic.html
@@ -38,7 +38,12 @@
                 { name: "OpenStreetMap", kind: "OSM" },
                 { name: "Stamen - Toner", kind: "Stamen", visible: true, options: { layer: "toner" } },
                 { name: "Stamen - Watercolor", kind: "Stamen", options: { layer: "watercolor" } }
-            ],*/
+            ],
+            // To show thumbnails in the base layer switcher, add a thumbnailImageUrl property:
+            // externalBaseLayers: [
+            //     { name: "OpenStreetMap", kind: "OSM", thumbnailImageUrl: "https://example.com/osm-thumbnail.png" },
+            //     { name: "Stamen - Toner", kind: "Stamen", visible: true, options: { layer: "toner" }, thumbnailImageUrl: "https://example.com/toner-thumbnail.png" }
+            // ],*/
             mapguide: {
                 agentUri: "../mapagent/mapagent.fcgi"
             }