I think your composition works, however, I think the figure could either go past the canvas border on the left side where the front of the mane is or moved to the right for a little more space. I think your colors are working, but the values are all fairly close. Currently, the harness is what stands out the most for me. I think this piece could benefit from more contrast; for instance, darkening some of the shadows and strokes in the hair. The drawing is pretty good, but maybe varying the line weight in certain areas such as in the mane to push it forward could be a nice touch. The lighting in some areas could be improved, such as in the mouth where the top portion would cast darker shadows over the tongue and harness. Also, the eyelids could use more shadows to suggest their shape and mass more. Overall, I think the drawing was done fairly well, your provocative expression was successful, and I really enjoyed the painterly strokes in the mane.