Well, you're going to be around 2.75-3.25WPG. Since you want to go low-pruning, seems like ferns and the like might work best.
I posted an article on autoDoing in the DIY section which might help.
I suggest Rummynose tetras because they school constantly and are very eye-catching (but I suggest rummies to everyone, so...)
I've set up a room divider 55G before. Here's a pic:

This was supposed to be viewable on both sides. I made some changes before tearing this one down, I removed the crypts from the front of the tank and tied 45+ baby java ferns to the driftwood on the right.
That's about all I have this early in the morning.
