Nice stuff. Really dig the skulls from last year. The first 2 images are awesome too. Doing master studies is sure way too improve. I don't know but your pencil lines look way better to me than your digital. Please keep posting.
So far you've done very well with your studies. I'd like to see what you can do without reference now. My only advise on your works so far is to focus on the relationships and depth. You should get to the point you're getting to when your finished, then zoom in even further and refine the details and edges it's easy to stop and say you've done enough, so try to work on more detailed finishing.
AdaptableSimon: You're right, been working on non-reference pieces but I'm too ashamed to put them up yet LOL. Depth and atmosphere have been a big challenge, maybe my weakest area. Thanks again for the advice!!!