I would get more snails and small hermit crabs, just a thought.
For fish, I like six line wrasses and dottybacks. Dottybacks tend to be a little more expensive though, depending on which you get. Arabians are really nice! One the favorite fish I've ever owned. Lots of people also keep jawfish, blennies and some gobbies in 30 gallon nanos. With 2 clownfish already, I would pick something that is going to stay at the substrate, or hid in the rockwork, clowns tend to get aggressive easy in nanos. Also, I would only pick up 1-2 more fish. 2 Clowns, six line wrasse, one other guy would be my suggestion.
More snails and crabs will help keep your tank clean with the added biomass, just get the cheaper guys and only ahve 1-2 ornamental crabs.