Here are a few others:
Stelis ciliolata (One look at Ron's plant on Flickr will get you hooked!) -
Stelis ciliolata | Flickr - Photo Sharing!
Available from Andy's Orchids - nice big plants. Not a true micro-mini, but the bloom stems are proportionate to the leaves.
Muscarella species
Rubellia (Pleurothallis) rubella
Dendrobium cuthbertsonii
Lepanthes escobariana - again, look at Ron's pic on Flickr:
Lepanthes escobariana | Flickr - Photo Sharing!
Lepanthes revoluta - available from J and L:
J&L Orchids ~ All Other Pleurothallids
Trisetella species - they're all awesome. I killed my hoijerii :^( but the others seem to do just fine for me in a terrarium.
Some of the "Big" Lepanthes are still quite manageable, and they're very showy: wendlandii, elegantula, pastoense, D'alessandroi, horrida, chameleon, hirtzii, etc... While they can be a little tall(5"), the leaves are still very manageable(1.5"), and they have an "airy" feel to them - you can see plants behind them because of the long skinny ramicauls. For me, they're a good use of space because of their big flowers.
Dryadella lilliputiana is really cute.
Soph. coccinea might be a little big for you, but when it's in bloom, everything else pales in comparison. Mine does really well in the terrarium with the Lepanthes.
Marnie Terkel is going to have some L. tsubotae soon. They're in flask now...
And yes, some of the Platystele are great. Some of them have really long stems, though - they can be a bit rangey..
Porroglossum meridionale is nice in a terrarium - not too big, and very cute.
Scaphosepalum rapax is tiny and awesome - a really dinky plant with proportionately large blooms.
Have fun with your project! Feel free to call or email any time to compare notes.