maybe a bit more consistency w/ the shadows, and maybe the balls can get some shadows too? i like this a lot and wish i knew more about design to help you kick it up a notch.
But that knotted section is bothering me. It doesn't really make sense as a knot. The piece that comes toward the head comes from the left of the knot, but it needs to come from the right for the knot to work. I'm probably just be picky! Still great job!