Some of the composition is a bit odd, like the blade of the sword being off-centre. You should also bone up on color theory so you know how to make the contrasting colors seem more natural with each other.

Hey it's the imgur guy! I would suggest try to avoid using fully desaturated colors (black, gray, white, etc. Otherwise known as "perfect grays"). Colors like these are normally very unnatural in real life and should be used scarcely or not at all. Instead substitute desaturated colors for perfect grays.