I really like the feel of your scene. The geometry and the lighting seems to fit well for me. I wonder if a little more randomness in the tiny debri lying in the foreground might look a little more realistic but not too much randomness. I think the tiny pieces look great at the size they are but they seem just a bit too familiar to each other, too much like they are all copies from the same piece of geo.
Don't be satisfied with what you can do but rather strive to do the things you can't do!