great progress of the concept over time, its neat to see such a prgress of evolution. The newest one is pretty neat indeed, nice use of color, but the wing still seems a little flat. Did you look at a lot of birds (anatomy) for reference? that always helps me a lot...
and see how nice your pictures are if there isnt blood in the paint? these are so much more awesome then the bloody ones...
i didnt use them for a long time, but at a certain point you notice its a verry nice way to work with. I mean, at some point you'll just get tired of your wing not looking like a wing and stuff.