The hardscape and the stand are top notch. I like the idea of having a single species of a low carpet plant - this tank has a lot of possibilities in what you can do. I would consider doing a moss wall in the background, not putting any tall plants, and having the low carpet plant in the open space of the tallest peak. Then in the back right corner put in a Crinum Calimistratum and its long flowing vines will eventually take over the top space. You would have only 3 plants and you don't hide the hardscape.
Do you have any plans on putting a background on the tank or do you want to keep it so you can see the wall behind it?