wowww, love the composition idea ^^ esp love those fingers pointing on Sol, and custom pixelated HUD haha.
as for criticism you asked, it's mostly on anatomy and perspective. most of the enemies on the top screen should've shown more of bottom view. secondly, you coulda use more orange/yellowish color for the highlight rather than white.
anyway sorry for being late on noticing your fanart! thanks for your drawing, do you mind if i post this (with link) to Stellar Arms FB page & tumblr? :D
~Laz