There is alot of things that I cant even think of that you could put as far as corals go. Well it depends how hard you want take care of and if you have good water movement or not. If you dont have a small powerhead you really should add one. But assuming you have one you can start on some easier things like maybe a leather or toadstool. If your tank is established well than I would say that you could have a clam of some sort to add color if you want also. My favorite is Purple Maximas but they can be harder to keep than someting like a derasa but are still a good choice. I love scolymias as well i personally have 3. one is dark red with a green center, one is orange and white striped and one is a solid light brown. Their is many other scolymias and almost none of them are exactly alike just find one that looks good.( be sure you see it open fully before you buy one). That seems like pretty decent lighting for some nice corals that are pretty hardy. I would just try to stay away from acraporas and things simular(hynophora, montapora, etc.) Thse require really good lights and super good water quality. You could also try some different types of mushrooms and polyps. The only thing i have a concern with is if you can keep the water quality consist on a tank that small. It all depends on if you are able to keep the water stable and if you can on a tank than small many things are possible.If you cannot keep the water decently consistant than I would forget alot of corals, but it is possible. Just be careful and ask alot of questions before you buy.