Osprey is supporting their popular Frostgrave rules with some paper model ruins for the game. They could of course also be used for a number of other medieval and fantasy games.
paper model
Papercraft Nativity Set
Schweitzer Comics offers a very nice paper model Nativity Set. It’s not quite free, but it is “pay a fair price.”
Free Paper Models: Laboratory or Alchemist Equipment Models for Your RPG!
For furnishing your dungeons, here is a set of models of alchemist / laboratory equipment free for the downloading.
Free Dungeon “Furniture” Downloads
Stock your dungeon with Heroquest style furniture! There’s lots of good stuff here for a wide variety of periods for skirmish battles.