One thing: The armpit's too stretched by that top line (the one that goes parallel to the top line of the shoulder), it makes it look like the joint protrudes. Compare to this pic [link] where you can easily follow the line of the elbow up to the shoulder joint where it then stops. I think the image would benefit without that top line and for the elbow-to-armpit line to curve towards the mid-torso slightly (like that of the hind leg's knee-to-hip line). I hope that makes sense!
That aside it's a great use of gradient and style!
Oh, I see what you mean! I can't believe I've never thought of how weird it looks. Thanks for the heads up! I won't be changing this image but I will definitely think about it in the future. Thank you.