Get rid of the damsel first. Then maybe a pair of clowns, a yellow tang, a coral beauty angel, a few green chromis, and a few pajama cardinals. this will get you some color in some of the smaller, more docile species. Check out www.drsfostersmith.com
to find out the eating habits , aggressiveness, max adult sizes. And you are going to need a lot more of a clean up crew. Maybe some urchins and serpent stars. The urchins eat a lot of algae and the serpent stars eat anything the fish and crabs don't eat.