I never can decide on what to get. I love the look of my tank but it feels empty and a little color imbalanced. I've got a really loose budget so give me some ideas!
I think you could use some height and some sway over on the right. Gorgonias? You've got a nice variety, needs some big eye-catchers like that sweet monti. I feel like tanks this size look great with a big Devil's Hand or Sinularia in them. And it may seem like it's old hat, but my coral guy has a big colony of pulsing xenia in the upper corner back wall of his display tank and it looks pretty awesome. I think xenia has a role to play in a tank like yours with all that color going, and it would be a fast way to fill it in.
You can use some blue/purples in your color palette - maybe something like a frozen lepto, some blue acans, dragon breathe favias, or just general blue color morphs of torches, acros, etc..