There are some executional problems with a lot of them (the unfinished quality of Thor, anatomical issues with Wolvie, the Girl with Guns on a Bed's face)...but those can all be worked out with practice. What I do love about these pieces is the drama and compositional elements. Those, you have a great eye for. I think that alone is worth a lot. Keep working on your painting/rendering and your figure drawing and you'll be a force to be reckoned with!
Looking forward to your next piece.
"Every generation sees the past though the lens of its own time." - Thom Hartmann