The algae eater will get VERY big, and they get a little aggressive as they get older, too. (That's what I've read up on them, not that I have one myself). If I were you, I'd take the GAE to the lfs and trade it for a few pygmy coryies. I wouldn't add much else to that tank though. Plus, rainbow fish need to be in groups, too, so you wouldn't have room for those.
JMHO.