My suggestions:
- Use transparency instead of that grey color which resembles the bg color too much.
- Use more contrast between colors because it is really hard to see what is going on.
- You could employ more brightness.
The design is really cool, you can improve this drawing. If you need better tools or tutorials you can check out my thread, which is a compilation of useful resources http://pixeljoint.com/forum/forum_posts.asp?TID=24744
Nice. i like how you made it look like heartbeast charecter from this vid https://www.youtube.com/watch?v=2o8OzyFl5gM