can be improved
1 the shape of the head seems a bit too wide and unnatural.
2 add shading, even something as simple as making one side of the sword's blade
lighter than the other would be an improvement. The hat is a cool shape, but is a solid flat color and needs some texture to it.
3 the hair is too repetitive and uninteresting, you could make a cooler hairstyle.
also, you could add a background to add to the detail and make it seem less blank and simple.