You can get away with 3 or 4 fish in there, but keep them small. Build it up slowly, and the rate at which your nitrates rise will tell you if you can be bothered with the water change regime needed to keep up or not.
Maybe look into cardinals as another option too. Royal grammars are great - bright and dart in and out of the rock. A pair of clowns would be fine - nice to see them interacting. Maybe a pistol shrimp + goby pair?
I'd avoid Xenia as it can grow very fast and be a nightmare to get rid of, if you ever wanted to (which a lot of people do). GSP is fine if you keep it isolated, or grow it up the glass - that can also spread easily. Look at kenya trees - I think you'll like them.