Yep, in little tanks as your first experience, I would go with pretty softies. So many beautiful options and they are usually very forgiving with water and maintenance. Looks great by the way. Love it when I do that deep clean on my little tanks.
Honestly, I would just add corals and leave the one large rock. You could get height from the right gorg, gsp up back wall, branching like a tree (nepthea or sinularia or toadstool). Ask before you get a gorg as if you want to keep anything except mushrooms, the wrong one will be too much for that little tank. I can recommend the grubes gorg highly (ora) cuz it is friendly, hardy, and pretty.