My concept is simple x ) What I usually do when I have an artblock is scribble it out on a piece of paper, usually with large, thick black lines. Somehow it gets rid of my art-blockiness! Try it and see if it works for you ;D
I love how you shaded with the pen. The strokes are very smooth and appealing.
I do think that something is a little off with the face. The nose should be placed down slightly, and the mouth not curved upward as much. The eyes are well placed.
Overall this is a nice piece, I love the details and the blotches of paint all over. At first it looked like blood which would have also worked with the pic, I think. The details in this piece are amazing. It looks like it must have taken a lot of effort.