Nike Air

This is not the real nike product, i just make this for practice about shading and texture. no pen tablet, just struggle with mouse and pen tool.
all the layers is vector shape in photoshop and smart object layer, so i can re-edit the style.
what do you think?
looking for feedback and critics.

here's the large preview http://d.pr/i/dwGP
here's the steps http://d.pr/i/mLWi