You asked for critique, so you'll get it. Don'tgetmadatmeplzplzplz. ><

As far as shading goes, it looks, well... okay. You had a difficult picture to shade; no matter what you did something would feel off. As it is now, the light source causes the face to look kind of flat.This might be the choice of colours as well, though; because you haven't been pushing the contrasts as much as you could, the picture looks dilluted, like it's been partially drenched in water so some of the colour wore off.
There is some nitpicking to do on the light source as well, I suppose, but that'll come to you as you practice.

I'll go a little into the colours and contrasts, because I think that's what really could've made it for this pic. You suffer from the same disease as I do; "contrast refusal". We don't really dare to push the contrasts, usually because we've already pushed it a little already and think to ourselves "that looks better than it did before I painted over it. Must be nice.". But the viewers HAVEN'T seen the previous image. They only see THIS one.
Contrast between the background and the character as well. Look at the picture greyscale; did you push it enough?
Also, the wings! So important. They need to really be darkened up.
And when I say contrast, I don't just mean light/dark. It's also in colours. Especially in the face, it's the most important part. Some blueish tones instead of the greys in the background can really make the character pop.
Cold shadows! Warm lights! Or actually, why not try a warm shadows, cold lights on this one? Sharp, blue light might just be what the picture needs...

You didn't ask me to critique the rest, so I'll leave at that. I WILL say this, though: remember that folds doesn't always have to end on the 'outline' of a character. They can be just creases inside the lineart.

Besides this, I really love it. It's an awesome idea, and it's moving!
Now go draw me summoar art! D8<