I like the overall design but it looks a little too unnatural to me. I would change the heights of each column so it isn't one level all the way across.
The design is whatever you like, I just see an issue because there is to much rock contact with the bottom. Especially those flat bottomed rocks. You really should try to limit the contact surfaces of the rock to the bottom, not for aesthetics, but for tank health. Those contact areas will receive no oxygen.