The rock work looks great! I keep on changing mine... can't seem to get it right where I like it
Anywho, some stocking ideas. I have a 28 gallon with approximately 30 lbs of rock (all live now). I have one green chromie (my first fish), one bicolored dottyback, one lil' nemo clownfish, and one yellow watchman goby. So, four fish, which some may say is too much, but they are small, neat, and occupy different areas of the tank. Plus, my water levels are stable, and nobody's gotten sick (yet). The goby stays on the bottom as it has no swim-bladder. The dottyback swims through the rockwork, and the green chromie and clownfish are BFF's in the upper half of the tank (they even sleep next to each other!). The dottyback is my absolute favorite. She has so much personality and zips in and out of every little nook and cranny. If I move something, she notices it right away and will stop to look at it and swim back to where whatever I moved was placed before. The she turns and gives me a reproachful look (seriously!). Aside from the fishies, I have a variety of magarita, nessarius and astrea snails. I have one conch (which is just the funniest thing. Some times all I can see is the top of it's shell and one eyeball poking up through the sand). I also have 4 hermit crabs, one green emerald crab, one cleaner shrimp and, my newest purchase, a decorator arrow crab, which is probably the ugliest and creepiest thing I've ever seen. I looks like a spider and, frankly, freaks me out, but I still love it. The one thing I'm missing is a pistol shrimp to hang out with the goby. I've just started getting some corals. I have one duncan coral and some button polyps. So, some ideas there too.
Also, I noticed that you said some crabs had hitchhiked with your rocks. Be careful with those, they may be bad for any fish you put (i.e. your fish may end up sleeping with the fishes in a bad way!)
Good luck and have fun!!!!