I just picked up some little bromeliads at Home Depot for 4$ a piece. They weren't as pretty as the big ones, but they're small, and hopefully will look a little better with some care.

Pothos is the go-to plant for vivariums, I think. Get a cutting from someone, or buy a small one at the store. It's easy to root. (It's another one of the plants I picked up today, yay for shopping!)