Fallen Angel

Your technique is nearly flawless. The loose rendering of the background and wings allows the eye to focus on the most vital part of the imagine: the shocking contrast between the innocence of her expression and the blood dripping down her chin and hands which I find more disturbing than doing a full on blood and gore piece.
The choice of blues and warm grey is a very refreshing colour scheme, as usually artists depicting fallen angels go for darker, bolder colours and racier designs. The wings look realistic and fluffy and the anatomy is spot on.
Although I admire the subtle touches that make this piece dark, my personal opinion is that they could have been a bit darker. The eye colour is good, but the shadows around the face, if darker, could have made the piece a bit more dramatic. Also darkening the right side of the background just a smidge, could have symbolised her transition from light to dark. But that's just me looking for a needle in a hay stack.
All in all, this piece is pretty fantastic. It goes to show that little details can decide the entire mood of the work, not just the colour palette or topic choice.