Yellow Tang will outgrow that tank eventually, so watch for health issues if you keep that. I would go with some kind of dwarf angel (whatever you like...so many and all look great)...maybe a Foxface...some kind of wrasse (again, so many to choose from)...maybe a group of Anthias...a Hawk.
It is always hard to give specifics, as "what kind" of Angel, Wrasse, etc as it is so subjective. Make sure you are getting fish appropriate for your tank size and the ones you ultimately choose should do fine. Check out places like liveaquaria.com for ideas and they also have compatability charts.