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.
Here's an idea for a miniature wargaming scenario: During WWII, a group of US paratroopers, or British commandos are sent to destroy a V-2 rocket base. Of course, to do this, you're going to need to add a model of a V-2 rocket to your terrain. This website has a free paper model of a V-2 rocket in 1/32 scale. You could easily rescale it on your computer.
Matt Fritz has some advice on printing and basing paper soldiers for your miniatures wargames.
There has been a surge in interest in playing "Battles by Gaslight" in 15mm scale. No steampunk miniature wargame would be complete without a land ironclad or two. This 15mm Land Ironclad paper model fits the bill. It is based on one portrayed in a 1903 short story by H.G. Wells. From Ralph Currell.