The only thing I can criticize are two things, and one of them is semi-based off of hypothetical biology. 1) the arrow shafts seem to thin. 2) the bow looks like a short bow, which isn't the greatest of ideas for combat, and is usually a secondary weapon. It can't be a longbow not drawn to proportion, as I doubt a unicorn would have enough foreleg strength to give it a good draw. The only thing left would be a recurve/compound bow which it is not (demonstrated by the fact that the tips don't curve back forward. Other than that, spectacular drawing.