Here’s a site with four very nice paper models of 25mm / 28mm half-timbered houses that would be appropriate for a fantasy or medieval town setting. There are “shoddy shops” a “posh place,” a plain half timbered house and a building that is more fantasy oriented. All are in pdf format.
Paper Models
Back to The Future Steam Train Paper Model
Paper Insider has a free paper model of the time traveling steam train from Back To The Future III. I really can’t tell what the scale is, but from the side panels, it may be ok for 25mm.
Seven Wonders Paper Models
Delta 7 Studios has a collection of free paper models of the Seven Wonders of the Ancient World: the Great Pyramid of Giza, Hanging Gardens of Babylon, Temple of Artemis, Statue of Zeus at Olympia, Mausoleum of Maussollos, Colossus of Rhodes and the Lighthouse of Alexandria.
Combat Utility Hovercraft Paper Model
Your science fiction troopers need a utility hovercraft to get around in. Here’s a nice paper model of just such a craft.
Chickenhawk Dropship Paper Model
For Infinity and other science fiction games, here’s a paper model of a Chickenhawk dropship. It comes in a couple of different versions.