Google has provided me the answer to my original question: The images on the Page Toolbar are whatever the largest image on the page happens to be. I assume largest means file size, but it doesn't matter unless you've ripped an entire map from someplace or used another tool to create it. I'm making my maps in the editor, and the page image is not helpful. What I would like: When the Page Toolbar is toggled open, create a small image of the contents of the map (this would probably have to be done server-side, so there would be a delay). Alternatively, do this when switching from a map which has been changed. Alternatively, as that would increase resource use and take some time to implement, allow me to either upload a small sketch of my map or select which image on the map should represent it.