Most people dont think to decorate their garage doors, but if you have particularly dull garage fronts, its certainly a possibility.
The folks over at Style Your Garage sell a variety of photo murals, designed to appear real enough that passersby will look twice, trying to figure out if thats whats really in your garage!
They offer landscapes, animals, and all sorts of vehicles (perhaps youd like the appearance of a jet in your garage rather than a boring old car) as well as rooms (such as a vast wine cellar).
Attached by Velcro, the non-permanent billboards take 30-60 minutes to install and come in a number of sizes. Theyre supposed to work on any material of garage door.
Prices run from $139 to $400 or so.