The proportions are quite nice. Many have pointed out the bent arm issues, but the left side of him I think his shoulder looks a bit too far away (where it comes to its highest point), as if it was actually part of his upper arm.
Also, I'm not sure how to say this correctly, but hopefully I won't confuse you too much, but also his clavicle area (from his neck to his shoulder) on the left seems to dip too low in comparison to the right. I know his shoulder would raise since his arm is, but I just think it needs a slight less slope. His thub is a little tiny too. Yes, I'm getting that picky, because fortunately for you, he doesn't have many anatomical issues. :] Nice job so far!
ie.
http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/19623.jpgThere's a basic structure of the neck to the shoulder. Hope it helps. D:
