I'm not qualified to offer advice but I do want to say I think you did a wonderful job. The ridge above the eye that becomes a horn look very three-dimensional and whatever technique you used for the texture works very well. Questions I would ask would be where is the eye line? Based on that the cross contours on his belly should be doing something... if I was a better student I would be able to tell you, but alas! I am not a better student... I'm not even a mediocre one. Hopefully someone with more knowledge and wisdom will stop by to lend a hand. Best of luck in you art making journey.