Here's my list of candidates thus far:
Adenium obesum - Desert Rose (bonsai)
Ananas comosus - Miniature Pineapple (psuedo-bonsai)
Anastatica hierochuntica - Jericho Rose (returns from dry dormancy rapidly after watering, seed-scatterer which may require pruning)
Aristolochia spp. - Dutchman's Pipe (scrambling vine, requires pruning, some species are subtropical)
Asparagus densiflorus (Protoasparus densiflorus) - Asparagus Fern and others
Bambusa ventricosa - Buddha Belly bamboo (requires pruning/root binding)
Beaucarnea recurvata - Ponytail Palm (psuedo-bonsai)
Caladium bicolor - Two-Colored Elephant Ear (local endemic, requires strict dry/wet seasons)
Citrus medica var. sarcodactylus - 'Buddha's Hand,' Fingered Citron (bonsai, showy fragrant edible fruit)
Coccoloba uvifera - Sea Grape (bonsai, may require harvesting, compact in sun)
Corymbia citriodora - Lemon-Scented Gum (bonsai, requires pruning, fragrant)
Cycas revouta - Sago Palm (psuedo-bonsai, requires root binding)
Equisetum scirpoides - Dwarf Horsetail (zone 3 - does it tolerate tropics?)
Eulophia petersii - Peter's Eulophia (psuedo-bonsai, succulent)
Euphorbia milli - Crown-of-Thorns (psuedo-bonsai)
Euphorbia tirucalli - Pencil Cactus (psuedo-bonsai)
Hedychium spp. - Sweet/Butterfly Gingers (fragrant white/orange/red flowers, large red inflorescences)
Heliamphora heterodoxa - Marsh Pitcher Sp. (tolerates high temperatures)
Hylocerus undatus - Dragonfruit (epiphytic, large edible flowers and fruits, may require pruning)
Kalanchoe gastonis-bonnieri - Donkey-Ears Kalanchoe (requires pruning/gemmae harvesting)
Magnolia grandiflora - Little Gem Magnolia Tree (bonsai, requires pruning but stays small, proportionately large blooms)
Musa acuminata 'Super Dwarf Cavendish' - Dwarf Cavendish Fruiting Banana (psuedo-bonsai, requires harvesting)
Nepenthes ampullaria, bicalcurata, gracilis, rafflesiana, thorelii - Monkey Cup
Pachypodium brevicaule - Tsimondrimondry (psuedo-bonsai)
Pallenis hierochuntica - False Jericho Rose (returns from dry dormancy rapidly after watering)
Platycerium bifurcatum - Staghorn Fern
Plumeria spp. 'Yellow Jack' - Blue-Yellow Flowered Plumeria (azure)
Polypodium polypodioides (Pleopeltis polypodioides) - Ressurection Fern (epiphytic, returns from dry dormancy rapidly after watering)
Rhizophora mangle - Red Mangrove (bonsai)
Sansevieria cylindrica var. patula - "African Spear" Sansevieria (night-fragrant pink inflorescence, fan-shaped growth habit)
Selaginella lepidophylla - Dinosaur Plant (epiphytic, returns from dry dormancy rapidly after watering)
Taxiphyllum barbieri - Java Moss (aquatic/semiaquatic groundcover)
Tillandsia spp. - Air Plants (epiphytic, blue/purple flowers)
Zamioculcus zamiiflora - "ZZ Plant," Jade/palm looking thing (psuedo-bonsai)
Zingiber zerumbet - Shampoo Ginger (large round inflorescences that go from yellow to green to red as they mature)
Some of these won't make the cut for reasons of size, expense, or upkeep. Specific varieties may change depending on whether or not I'm supposed to work with certain colors or something; I haven't got all the details yet. I'm also thinking about adding some microfauna. Does anyone know where tropical dragonfly cultures can be obtained? I'm sure there will be the occasional fly or mosquito or whatever, so I thought it would be nice to have some proactive controls. Odes seem like a cleaner control species than goldfish, which would be my second choice. I'm curious about Halocaridina rubra - the Opae'ula or Hawaiian Micro-Lobster as they're marketed - and Golden Apple Shrimp as aquatic grazers.
I still need to pick some ground cover species. Utrics are tempting but would probably run rampant. Same for pygmy Drosera. I've been thinking of ways to contain them by planting them in areas bounded by totally dry gravel or moving water, but they probably just won't see a lot of use. I think I'll lean towards rosetted 'dews for the round-and-petite look. Mexi-Pings will definitely have a place in the area, but I'm not sure which. I'd like to use a fairly diverse selection. Are there any orchids that keep compact foliage and clump over time?
I should have a schematic of the room soon. Thanks again everyone.
~Joe