I think your art is wonderful. Some people have a real problem with people who succeed when they "break the art rules," such as "don't draw/paint from photos." Who cares if you use photos? You talent is obvious in all of these pieces.
The only critique I can think of giving is that the background of the tooth piece looks a bit flat. Perhaps that is due to the lighting of the photo, though.
I think you're doing well. If you want to experiment you can always ask a friend or someone to pose for you for a few minutes every day so you can draw from a living model. Or use a mirror and draw yourself. I don't think that is necessary, though, but drawing from a live person does excersize your abilities in different ways.