Your head seems to be lacking shading and detail.
This is how I made my ninja head:
Start with a sketch...
Then, add shading and detail..
I watch Vitiek's speedpaintings and I watch some "sycra" on youtube, it helped me make the textures look good. I suggest you watch some tutorials by sycra.
Last edited by P4P4Z0LA; Jun 27, 2016 at 12:35 PM.