Fairy wrasses can provide a nice splash of color, they're fairly docile fish though.
Royal grammas are nice and bright and are a bit more territorial. Not sure if they're ok in a smaller tank, perhaps someone else can chime in here.
Some of the dottybacks are brightly colored and can be more territorial and sometimes don't do well with more peaceful fish.
Firefish are nice calm fish, pretty timid but beautiful. They will often jump out of open topped tanks though.
There are lots of neat gobies and blennies, most of which are reef safe.
I find it easiest to either look through my reef fishes book by scott michael or surf this site
http://www.liveaquaria.com/product/categ.cfm?pcatid=15 to see whats out there. Then post here for peoples experiences with specific fish you're interested in
