Sorority tanks usually end up being more about the safety of the fish than looks, haha, it's hard to avoid the stuffed look you'll end up with. You should really try to find a way to fill in the top section more--all bettas must go up to the surface to breathe and this is also were they go to eat, so squabbling near the surface is inevitable. Floating plants should help with this. You should try ordering online, often the prices are a lot better and you have a much nicer selection. You might try Big Al's online: http://www.bigalsonline.ca/BigAlsCA/...wType=Category
Also, you might want to look carefully at the skull ornament--I've seen a fish get stuck in and mangled by a very similar (if not the same) ornament. I recommend stuffing the smaller holes with plant matter, filter floss, or filling it in with aquarium silicone. Injuries from getting stuck can be really nasty, and during a moment of fear a fish can dart into some very sticky situations.