As for hanging stuff on the walls, this works very well: Loctite, Fun-Tak, Mounting Putty (Google it). We have used it on just about every surface. It works and never leaves a mark. It says for use up to 1 lb but we have hung much heaver stuff with no problem (even being bounce around on the ocean). It is also very good for keeping things like lamps or ornaments in place on a shelf.
Mark and Cindy
s/v Cream Puff
http://www.creampuff.us