I really love the colors in this. I like the way they compliment each other. The character and the scenery work great together.
I would suggest turning the sword a little so you can see more of it.
I like the soft whites and blues against the strong and dark black, purple and blue. It is a good contrast.
I feel that if you were able to define the background and the foreground a little bit more the image could be stronger. I wouldn't suggest changing anything. I would just put a little emphasis on distinguishing the background.
Other then that you did a great job and it is an amazing image.
I certainly would like to say that this cosplay is fantastic. The colors work together really well and the photo composition just makes it stand out all the more from your average cosplay portrait. The facial expression and the stance of your body in particular makes this look more like a still frame of a video, and it really looks as if you've made this cosplay actually come to life. I love it. It's a very creative and inventive take on a cosplay with an amazing choice in background and coloring. I definitely give you major props for bringing yet another great photo to the cosplay world. Kitty~