there are a lot of aquarium plants (most of them) that can be grown terrestrially or emergent. they're all suitable size for terrariums also. many have qualities many of us are looking for. some have beautiful inflorescence or variegations that don't show up in submersed growth.
some examples
java moss (duh, right?)
java ferns (there's several growth forms including trident, narrow leaf, regular, lace, etc.)
bacopa species (monnieri has been proven for sure to be a beautiful foreground/transitional plant that will stretch out over the water and provide shade and allure)
riccia (ok, stating the obvious again)
several cryptocoryne species
most, if not all anubias species...
check out the plant finder at apc...
http://www.aquaticplantcentral.com/f...finder/all.php
when you click on a plant name it should tell you if it can be grown emersed as well as some other details and a short history lesson.
also, see what tropica has. i think they typically just deal with aquarium plants but they grow and sell a lot of their plants emersed. not only can you find a lot of plants from them but they might tell you what care they'd need for emersed growth and save you a lot of guessing.
there is a lot in the aquarium hobby that just isn't explored too often. hydrophyte from ripariumsupply.com has done some things and always gets good feedback, but that's about the only person i know really delving into the transition back to land.
many of these plants grow on land or in tidal areas in the wild and are just acclimated to submersed growth so it shouldn't be a far stretch at all. also even though many of them are pretty common in the aquarium trade it doesn't seem they're offered too often for terrariums. many people fear acclimating a plant from one environment to another or just don't know what the plants are capable of so will avoid purchasing "aquarium plants" for other setups. if you were to offer them grown emersed in a market looking for emersed growth surely you'd be able to catch a market that doesn't know it's already there...