You seem to fall short of capturing the 'movement' of the figure holding the mask. Part of the reason is because he's not balanced correctly...if you'd like me to redline, I will, but overall a book that will help you immensely is
The Animator's Survival Kit. It has some good info on line of action and things like that.
I mention movement because it's a very important part of comics, is the ability to convey motion in a still picture. Also body language in general is very important as it can be used to tell half the story.
I'm kind of in the middle on whether you should do a comic or not. On one hand, Kupo has a really really good point. I'm pretty sure for me, focusing on improving my art while doing my comic stunted my panelling and pacing skills initially. On the other hand, doing a comic really helped me get in loads of practice for my art.