Force Icon for Map on Page Toolbar?

I notice when I construct a map from scratch and use various smaller graphics to create the map background for the game, the icon representing the map may not be very representative of the page, since I did not use a large map background image file. Is there a way to force a different graphic on the map to be used as the Icon representing that map on the Page Toolbar?

Yes.  Zoom out to a reasonable view of your map.  Screenshot it, upload it to the map layer, resize it to be larger than any other graphics, then send it to the back.  It won't show up on the map, but the icon for the Page is always the largest graphic on the Map Layer.

emphasizing what The Aaron said, the Page Icon is generated from whatever the Largest (stretched) graphic is, on that Page. You can put an image in the background or margins, and stretch it larger than anything else, that image will be used for the icon.

That worked beautifully, thank you!