If you were to angle the box just slightly, you could add a lot to the portrait, in terms of interest and realism.

In general, I think angel wings sprout from the back. Also, as it is, the wings you have are shaped(the coloring doesn't hurt it XD) in a way to invoke an assumption of their being fins. As well, your lines all over could really use some cleaning up. The jeans seem to be part of the shoes, or vice versa, add a bit of difference or show some sock. The jeans are one of the better aspects of the piece, but they have very jagged edges and are far worse at the bottom than at the top.

I notice that when you zoom in on the arm, there is a little vein of black down the center, but it starst and stops on each side very abruptly. The blackness between light sources works well on the legs and torso, but it gives the arm a look like it's an extruded bent square, if you get my meaning. To make it a bit clearer, the black line makes it look as if it has two facets, one reflecting each lightsource.

This is pretty good but for a few areas. The head is lacking some definition and is a flat color on the sides; add some details there. The majority of the piece is top-lit and shaded accordingly, but the upper body is lit from the front and pillowshaded.