Nice works, but
I do not like the skull in the fund, but the quality of edition and computer graphics they are enough good. In my opinion the fund is what it trumps, it would be better to prove with another drawing or photo, ej. ship, island, something more real.
And too, you must calibrate well the luminosity since there is seen the difference between the light that falls down on Keira and the one that is illuminating.
But, nice work, still like that and you will improve your skills.