Design your shadow shapes more deliberately, don't be afraid to go darker with your shadows. With the top right image the upper arm looks too short. If it's supposed to be foreshortened and going towards us, it should having more indications of doing so. Otherwise it will just look like his upper arm is too short. You might want to use less lines to indicate clothes if you want to shade it as shadow and light shapes might indicate it better and clash with lines if there are too many. As for back anatomy, deltoid muscle goes on top of scapula not below it. | Artwod Feedback