There are a lot of superhero miniatures rules out there — both free and commercial. So if you want to try one without going to all the trouble to paint some minis, you could try some of the paper figures on this page.
Matt Fritz has some good instructions for drawing your own paper soldiers. This would be a good way to try out a new period!
Clifford Button of Paper Tiger Armanents offers a free 1/72 scale brick structure. It was inspired by a building in the Strand district in Galveston, Texas.
Germy’s World has some nice paper models for 6mm science fiction gaming. There are tanks, drop pods, a mega drop pod and a drop ship. These would be useful for Battletech, or Reaper’s CAV, or Games Workshop’s Epic 40K.
Germ’s World has a large collection of paper models for wargames in 6mm scale. These would be useful for, say a BattleTech game, or maybe Epic 40k. There are hangars, moon bases, factories, space docks and middle east buildings.