The sig looks almost monotone to me, despite shades of colour used, and the slight red theres no real contrast in the piece, which makes it look dull in my opinion. I would work on bringing some realism into the piece, such as changing the lighting, so parts like under her nose would be slightly shades, and under her eyes etc, the face looks slightly pixelated if i look at it in more detail, maybe blur some parts of it. The perspective and flow of this piece are nice. I don't know, it's a nice piece, and hard to criticise, the only thing that it is lacking is some real depth, i would just blur more the the dark greys on the left side of her hair, and see what you can come up with doing that.
Nice work man.
He Who Dares Wins And i'll die to win, cause i'm born to lose Fucking Civilian