It's a nice design but it lacks power. If you had drawn the same thing in photoshop using more saturated colors and used some neat texture brushes; you would have gotten much higher marks. If you can draw like this on paper, you'll find photoshop or Painter a much better place to spend your time. I know because I just posted my very first Photoshop drawing (yup, a frog) and it was soooo much fun. I used about 12 different brushes to achieve the textures. Good luck. I generally like your work.