i disagree that its over defined except for the zip, i'd make that a little less apparent.
I think the folds need some work though, my fav ones you've done are on just the shoulders, other than them im not really digin them that much, remember to think about how leather folds, its thicker than cloth and more rigid, that makes bigger stiffer folds, also remember the key parts where folds occur, folds are gathering of material. You have to think about where tension occurs and where the material will hang of it, like the back, the back will have little/ no folds at the top because the material stretching across the upper back because its hanging off there, thats where its supported from, but further down as it hangs the cloth hangs and and it gathers at the bottom in mostly vertical folds (like a curtain). However this is effected by posture and movement, twisting the body will make folds appear diagonally from the shoulder to the opposite corner mostly. Anyway, main points where folds occur in a leather jacket is around the elbows and the armpits. meh, folds are unbeliably complicated imo, i still hate drawing them... maybe this tut will help you: http://www.cablenet.ne.jp/~japanime/tutorial/clothingmain.html
didnt see teh update >_<, it looks nice but shaddows should be less saturated than the main colour unless in percific lighting, this is why using multiply brushes can be a bad idea because they add to the saturation. The most saturated part of the skin should be the point where the light transfers to dark
It looks like your going for cartoony on the flesh, if thats the case then that part looks fine, maybe just some more color variation because it looks flat right now .
I think you need to make the folds less defined, cotton doesnt really have a big amount of folds and the shirt look like it fits small anyway. You can get a good idea by looking at your friends skin, notice that his folds are not defined very much at all and it looks great.
The only thing I see wrong now in the last image you have shown, is his eyes. I don't know if it's the skin or the model, but they're too...open, squall's eyes are more skinny, and they're a bit further apart. (And ask your friend to send me that effing model, it's hawt. XD What's his SN? I want it, so I can skin the hair, and try to compile.)
How did you make those arms? Did you poly model or plane model? I can't follow your stickied tutorial, the arm part. It's confusing So, if you used a different method, please explain to me ^_^ Thanks.