Here’s a treasure trove for you science fiction miniatures wargamers: The Starship Schematics Database has illustrations of hundreds of spaceships form the Star Trek, Babylon Five, Space Battleship Yamato and Battlestar Galactica universes. I think these would particularly useful as a source of illustrations for home made counters for your games.
How big is a Stardestroyer compared to a Romulan D’deridex? Which is bigger, a Vorlon cruiser, or Farscape’s Moya? This great site has size comparisons of the great ships from science fiction.
The Heavy Metal Wargaming site has some counters for use in starship games set in the Star Trek: The Next Generation universe.
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.