According to BrickFair, Simon Liu and friends at ToroLUG created Habitats, a simple standard that anyone can build. Based on the collectible series, each minifig is given its own Habitat befitting its character, time, and place.
Pick a favorite fig, build his or her Habitat, and bring it to the event to join the others.
There are two standards for Habitats. Be sure you are using the one your collaborative is using or your habitat will not stack properly with the others.
BrickFair Habitat Standard (3 wall Habitat)
Alternate Standard (2 wall Habitat)