Dyson Logos has created ten business card-sized dungeon geomorphs for free personal or commercial use. Dyson writes that when printed “on the backs of your business cards, the cards themselves become strangely collectible too, as people will want to get the various designs to increase their assortment of dungeon pieces!” Each piece has exits in the middle of each side to allow for orienting the dungeon complex in either a basketweave pattern or a block pattern. Going to an online business card printer like Moo will let you place different images on the backs of your cards.
These cards were released as part of his ongoing Patreon, where he creates maps and adventures for fantasy RPGs.