The Toposolitario site has a nice selection of paper models of mecha suitable for steampunk, pulp or wierd WWII games.
Minifight is a silly little humans versus monsters game.
Fat Dragon games offers a free 3-D paper model of a small wagon.
In 1/72 and 1/48 scale, here is a downloadable model of an Albatross DRII.
The Toposolitario site has a very nice looking downloadable gaming mat for futuristic scenarios.