I really like the shading and highlights on this drawing. The blue-purple shadows from the natural light look great in contrast to the yellow highlights on the right. And the shading is just overall very well done, the way it follows all the different shapes and textures. The fact that the lines aren't solid black give the drawing a very nice and relaxed feel, too, and make it more visible against the black background. The one thing I would recommend working on is staying inside the lines a little more. There are some places (most noticeably around the nose) where the color strays outside of the lines and it shows more in full view.