That looks great! Making the cave was definitely the touchiest part. I bought three packs of the larger rocks from petsmart that had several big flat rocks in them. I had to kind of do one half of the cave at a time and let it dry before I could layer the other half on top of it. Waiting was definitely very hard.
So far, so good on mine. I have a powder blue gourami that likes to go in and out of the cave, so I think something like this in a larger tank with a territorial fish like cichlids would be pretty cool. If you were industrious, you could build several small caves around the tank for a larger population. I bought four ghost shrimp to test my gourami's appetite for live food, and so far he ignores them. There is one shrimp that constantly swims up and down the front of the tank and the gourami just swims around him looking for food. I have my cherries on the way, so I'm hoping for a good match when they arrive.
I bought two african dwarf frogs yesterday, and so far they seem to be getting along as well. They LOVE the rocks. The only problem is you can see them in the tank, they're always hiding. That's actually the only big concern I now have about this project, there is room for critters to get in and around and behind it. The shrimp aren't a big deal, they're small crawly things that can really use this to their advantage for breeding/hiding/molting. Larger fish are a concern though. I'm afraid one might get behind it and get stuck. I was able to find on ADF this morning, but not the second. However, given the wealth of hidey holes, I can't really draw a conclusion from that. One big annoyance is this tank, when it was set up prieviously, didn't have a background, so you could see through it. Now it has one...but that keeps me from checking behind the rocks! Now I don't know if I should maybe cut windows in it or what. I'll have to see how desperate I get.