That is pretty cool. Couple things I might change if I were you:
1. Get some of the rock off the back - This helps prevent dead spots, and allows fish to move around without being seen. (Which will make them feel more secure, and theoretically come out more)
2. Do build up some...right now it looks like a shelf.
3. Build caves of different sizes. It seems right now like you have a goby tenement. Some different sizes will make other fish happier.
4. You want the smallest footprint on the bottom of the tank as possible (within reason, you also want it to be as stable as possible.) The reason for this is again preventing dead spots, and eliminating areas where detritus can accumulate.
Looking forward to seeing what you do with this.
PS - drilling rock with a masonry bit is not that hard, and I used zipties (cover in coraline algae very quickly) to connect them. This created a very unique, stable rock work...and I suggest it to anyone scaping. GL!