Paint is fun to play with. I've noticed, though that by placing the red plant at the opposite end of the rocks, that you've created two strong focal points. Tanks should really have one. If they do have to, the focal points have to complement each other, which yours do not. Just my two cents, otherwise, has the makings of a strong layout. The wood horns will soften with plants. You're going to attach mosses, right?
Liz