If you want to make the costumes looks even better, I would suggest taking the visible snaps off Dean's jacket. If you feel you are up to it, you should also either move the buttons on Sam's jacket to the other side (because the way it is now is girl-style) or, even easier, just take them off entirely to mimic a zip-up look.
In some of the earlier pictures, Dean looks like he has a serious case of giraffe neck. I think if you gave him a collared shirt, it would balance the length of the neck and would also match his signature layered look better.