These are some strong pieces. I can see the techniques you used and the way you used them is really skillful. It looks really good, I would only be picking my nose and smearing it against your drawing to make any other problems to pick at. ( lol) Anyhow,more in depth I would want to say there is always more room for improvement. I'd say the borders are a little distracting for me, I like how the frame outlines the faces, but it doesn't seem to continue through the rest of the piece. Somehow the border sort of becomes the frame and outline of the faces, which to me is not much of an issue. Great work!