Here is a list of plants my husband currently has growing in his Spec V with the stock light:
Water onion (bulb)
The various types of aponogeton you get with the "betta bulbs"
We just put some Blyxa Japonica in there, so far so good
I would do some Anubias and/or Java fern on the wood, as long as you don't mind trimming (they grow a ton of leaves and flowers depending on the kind) the "betta bulbs" are nice and both our bettas enjoy hanging out on the stems and leaves to relax near the top. My husband has put a clump of Java moss on a suction cup and placed it in front of the outflow to lessen the flow for his betta and he's much happier.
As far as tank mates our bettas are housed with nerite snails and ghost shrimp and everyone does fine. It will depend on the betta of course and if you do shrimp moss is a good idea so they have a nice place to hide. We even put a couple RCS in with my husband's betta and he doesn't hassle them too much. Just try and get the smaller ghost shrimp and keep an eye on them. I had one a while ago that would jump onto my betta's fins and ride him around, it didn't end well. I'm thinking maybe it was a macro type. Luckily my poor guy's fins have healed as well as they could.
Some other Spec V tanks to get ideas here also: http://www.plantedtank.net/forums/sh...highlight=spec