Nice aquascaping there. At first glance, I said "Wow, looks much bigger than a 30 gallon tank". If you can get that response from someone looking at the photo, you did a real good job on your arrangement.
As far as a final fish to add, I would steer clear of dwarf angels. I know it is tempting, but you have a heavy emphasis on your tank being reef. With the small amount of space, picking on your corals will be very likely and I'm not sure if you are willing to make it worth the risk.
A sunburst anthias would be a nice addition. Or a fairy wrass of some sort.
where's me money