I would personaly make the lines thicker, and either make the body a little shorter or open up the wings a little. It looks a bit too plain to be right now, and that would give it some energy.
Also, with the style you're going with, you might want to remove the lighting effects, they look out of place. Solid colors would suit the overall look better. And don't be afraid to go a little less realistic, stylized tattoos are the best.
As for the spots, the biggest ones should be in the middle to give it more balance. The big spot in the back looks a little awkward to me.
Edit: The head doesn't have to be completely round either. Give it a little more shape. The black part of a ladybug actually has two parts, the head and a portion of the body. You don't have to represent that completely, but making the head a little less round would give more dimension to the overall shape.
