Not sure if you agree or not, but the axe looks slightly distorted. If you don't notice this, study the reference more. Coincidentally, the part that is distorted is also the part that is not visible on the reference.
If this is only a model, I might suggest that you make the character off-centered or something. Putting a character in dead center of the page is not very creative.
Try coloring it once you fix the axe.