The part that stands out the most to me, is the armor. I think you did really good on the shading and lighting with the RDM armor. I also like that you put a lot of color in this, makes it very vibrant and because of the light and shadows you played with, there's quite a bit of depth.
The only area that I would recommend playing with in the future, would be the coloring on the RDM's hair. It looks like you were going for a particular style of coloring where there isn't much blending between the different shades and a few of the shapes in the hair seem just a bit off with the direction of the hair. Maybe adding a bit more curve to the shades?
But anyways, thats just a suggestion to try playing with to see if you like. Other than that, i think you did a very good job. The pic turned out well.
