This is a great piece. The composition is very interesting, the mixed media/layering is very successful, and the piece has very good balance. In order to improve the piece, you could think about developing the bicycle a bit more (more detail and contrast, especially within the wheel of the bike). Also, perhaps you could extend some of the layering from the top to other areas to unify the piece a little better. Awesome job!
And I forgot to add..I am an AP Student at Forsyth Country Day School in North Carolina (teacher: Rebecca Stone-Danahy)