Character Reference.

[GrooveMan.exe]

You should be making some lineart changes before you get too into shading. His arms are very mismatched in length, and the 'fashionable' asymmetry with the sleeves makes it even worse. The way the shirt hangs makes it feel that he's not actually wearing cloth; more like some kind of jelly/plastic substance. Even if he's wearing skinny jeans, they should still have folds and creases at the knees (actually, what knees?) and around the ankles, unless they're like; physically grafted to the bone.

In which case you might as well just make it flesh and stop trying to be faux-trendy.