what are you using for a background? it looks cool!
Years ago, I saw a street artist use spray paint and create something like this. He took a couple of colors or so and sprayed layers on a board (heavy construction paper). Next, he took a couple different ized bowls and placed them upside down over the colors. He then, sprayed black over the whole thing. He kind of blocked the white so that it dripped down on it to create the stars. In between each step he would take a certain paint can, light the spray on fire with a lighter, and held it over the board. He then lifted the bowls and there you got the planets. I actually, tried it a couple of times myself. There are some other affects he did like while the paint was still wet, he'd smear it in a way to create mountain peaks or other things.
The one I used for my background was actually from an old roommate. I had it in storage for years and finally got it out to use for my backgrounds. I will see about showing the whole thing soon, as well as, the ones I did. Maybe I'll do a step by step of the process as a tutorial this summer. hmmm.