Drawn

James Gurney, creator of the Dinotopia series of books, has a blog chock full of tips, tricks, and behind-the-scenes how-tos and whatnots: Gurney Journey. Included is this handy tip on creating a backdrop for models out of a refrigerator box:

Paint one side of it with flat white latex, and the other side with black. You can glue flaps to the top to make it taller. It will stand up anywhere and give you a simple light or dark background.