I really like the idea for the tree-thing! Are you doing it all in zbrush?
I'm not sure if you want critique, but if you do, it seems to me with the dryad-creature that you might be starting high detail a bit soon, before the basic shapes are blocked out properly? Like the brachialis muscle on the arm looks a bit too prominent maybe? I don't think you'd really see that muscle on such a delicately built person. Maybe you should work some more on a lower res, before going into that much detail?
Don't get me wrong though, looks good so far