I saw this post about an hour after you posted it, and have been thinking what I would do

if this set up were mine. Very nice

set up by the way. I decided I would make it a Pistol Shrimp with an attending Gobie of some sort. I always have liked the idea of having a Pistol shrimp, Gobie combo but have read the Pistol shrimp can do some damage to other critters in the tank. Don't know if thats true, just what I have read. Anyway thats my vote, seems like this would be a nice size tank for that, any bigger and you might not ever see them. As far as corals for the tank, might be a good place to put some of your SPS frags, kinda like a growout tank of sorts.