Crypts are nice but be careful with some species and cultivars like zonatus, fosterianus, trifasciata and 'red star/pink star'. If they don't get enough light exposure coupled with too much moisture they can grow straight up leaves that can reach 11" long as with what happened to my fosterianus & pink star.

Tillandsia would be your next best bet for small growing bromeliads. Species like T.setacea, xerographica, 'rosita', fasciculata, argentea, bella grow quite manageable (usually under 9" diameter/across).

There is also this very common bromeliad that produces branching bases that is like 3 inches high and 3.5" across (forgot what it was called probably an Aechmea gamosepala cultivar) that would probably work with your enclosure size