Here's some inspiration for you: Ken Hamilton built this and it was in Scale Auto a few years ago. Tons of detail, a really cool dio, it is what immediately came to mind when I read you post.
http://public.fotki.com/khamilton/models/open_road_camper/
Also, both Evergreen and Plastruct make several styles of siding in styrene sheets. Search for their websites and you can do a product search from there, if you can't get it at your LHS.