You've got plenty of choices ... many will depend on what you're looking for from the tank, and what your fave fish are.
A few I can recommend from experience, and which I enjoy in my tank (in no particular order...):
Wrasses - Flashers and fairies, along with the leopard. Active high in the water column, constantly on the move. Flashers generally come in an orange-red color, with spectacular finnage. Fairies come in just about every color of the rainbow. Some get along well, other species can be more aggressive - there are a few good resources out there on which is which. I don't know the Vrolik's, so can't say whether he'll be aggressive with new wrasses . . .
Damsels - some (I'm looking at you, Dascyllus and Abudefduf...) are highly aggressive, but I keep a trio of azure damsels that dart hither and fro, and generally don't bother anyone who's established. They can sometimes be snippity with new kids on the block, so maybe add them late in the stocking order. I have heard reports of Chromis (which are damsels, after all) not getting along well with other damsels, but in 210 gallons of water, they should be able to stay out of each others' way.
Dartfish - I've got a firefish and a zebra-bar dart. Not really "active", they mostly hover in one location, but very peaceful and pleasingly colored. Blue gudgeons are another option, which I started with but lost (Ich and carpet-surfing). They offer a charming sky-blue, and will hover in groups.
Blennies - "But I've already got one, and they don't get along!", I hear you say. There are a lot of different varieties, and I have both a starry and a midas in my tank. They're doing very different things, and completely ignore one another. The midas provides a pop of yellow and a flurry of motion in midwater, while the starry rock-hops and tries to avoid my kole tang. (Tangs can view blennies as a competitor for algae, but again ... 210 gallons offers a lot of room to maneuver.)
Gobies - I've got a yellow watchman in the display and a trio of blackray shrimpgobies in QT. They're small, and add movement down on the bottom. Clown gobies would do the same higher in the rockwork. Neon, sharknose and yellowline gobies will offer a cleaning service to any fish which desires it. Speaking of down on the bottom . . .
Dragonets - I keep a pair of ruby scooters and a target mandarin. Even in my busy tank, they seem to find plenty to eat, and add entertaining, gliding movement and color to the spaces in the rock.
Anthias - Some can be aggressive, some can be delicate. I hadn't planned on anthias, but my LFS got some Bartlett's in, and they swept me off my feet. Only been in QT a week or so, but so far, so good! They do want to eat several times a day, something to be aware of.
Royal gramma - Tend to stay close to home, and home is a bolt-hole in the rock. They'll defend that hole, but generally not too aggressively.
Angelfish - If you're willing to accept the risk, (many of the commonly available dwarfs seem to run about 80% safe) they add color and movement and a billboard of a shape to the area just above the rock. Genicanthus are reputed to be almost 100% safe, but I've no personal experience.
Don't forget the fascinating inverts! I keep the above with urchins, serpent and brittle stars, hermits, snails, several different shrimps . . .
Have fun with it!
~Bruce
