Upload Background Images

It would be nice to be able to upload images as a whole background.

Example: I draw out the outline of a dungeon on paper or another app. Then upload that image into the app as the background. Then in the foreground I can brush the texture inside the rooms.

Allowing me to take a premade dungeon such as that on dungeon crawl and basically quickly make it a battle map. And not have to try to transfer it over by counting grid squares and such.