Well, it is really bright on the left side, so that shows as just a big white area, and I do not know if anything is supposed to be seen there, but if not, I would fix that by putting something in (a design or a small fractal/c4d, maybe?). It could be a little less sharpened around the sword and render, but not too much, because that looks good. I personally would have put more of the render in, but the way it is now is alright. It could use a little sharpened under the sword and flash. The colors are alright, but there could be a little more. Tone down the brightness on her hair, and tone up the brightness to the top left section... Hmm... That's about all I see right now. Maybe add a small bit of text, too although I do not know where it would work. It's an alright piece of work, but it isn't amazing, yet. Keep it up.