Quick edit, I'll change my post after dinner with some more info 
Actually not, I must sleep now, but I'll try to do it tomorrow morning
EDIT: So, here goes...
First, thanks for the C&C, everyone. It's really great to get all this feedback from you
big brother: I read your comment yesterday morning and i thought "wow...I suck." So, before going to school, I took my father's anatomy books, so I could study them a bit more deeply. Of course, I was aware that those top two abs exist, I have a body (duh!), I just didn't draw them because no one seems to pay atention to them (Marvel, for example). Well, I'm not sure if I understood all of what you said, but I tried to fix most of it. He's got nipples (I remembered that at some point, but then I forgot
thanks for reminding me), tried to fix the collarbone thing (although I don't think I understood it), fixed the abs thing, his right bicept is now a bit smaller and tried to define his arms lines better (although I might not have done it well). About the headphones, you are right, they're supposed to be just a ball with an antennae (for more weird headphone designs click
here). And that's it. Thanks for the constructive critique, it was very helpful.
Indigo: I'm glad you like it. It's not that original though...It's just me, with a bunch of muscles and an odd headphone. I hope that feeling of flatness you and I enjoy in it hasn't been lost in my last edit
Helm: Although it was obviously very rushed, your edit helped me a lot, especially in the arms. I don't agree with the your folds flow in the jeans, though. I mean, if he was using them normally that would be the right way, but he has pulled them a bit downwards, which breaks the "natural" flow of the folds. About the colours, I don't think I will change them...I'm really liking the jeans without higlights and I'm still not sure if I'll keep the highlights I added on the skin. I'll wait to see what pther people think about it...it was very clever to unify the two darkest shades though. Again, thank you for taking the time to answer and for editing the sprite.
So, here's the lastest version, with all the modifications mentioned above.
