If you are going for a peaceful tank, I would avoid damsels. Damsels are very pretty fish but can terrorize some of your other fish. As
@john.m.cole3 said a blenny would be nice. The midas or bicolor he mentioned would swim in the mid portion of your tank. Hawkfish perch and are entertaining. Check out the longnose hawk that
@Shelby Rose suggested or a chubby flame hawkfish. Look @ gobies to add a bottom dweller! Some R2R members have a Wheeler's Shrimp goby. Every time I see a photo of a Wheeler's , I want one!
Look
@Live Aquaria for pics of any suggestions. It will give detailed info on requirements too ( feeding, temperament etc).
Before adding more fish post your "wish list" or stocking list. R2R members will check it and also advise you on the order of which fish to add 1st (or last) on your list.