The Haunted Dimensions site has paper models of three small crypts. The only downside of these is that the back of the crypts are defaced with site advertising. Still, there’s also a brick wall there that you can paste the crypts up against.
RPG Now has a free horror RPG module called Dead of Night: Night of the Santa Claws. It’s designed for the Dead of Night RPG, but no doubt could be modded for any other system.