I guess it is not bad, some nitpicks:
on her right here, there are some white lines and spots, which are kinda bad overall.
on her ribbon on the upper left is jagged, which is visible under all the simplicity.
on her skirt and below is also extraction problems.

because of the BG being so simple, it makes the character stand out a lot, which means, at this point, one would notice the character more than the BG, I am not sure if that is what you intended, but if it is, you should try harder for the extraction.
Overall, it is easy to view with, and thus, a great wallpaper for those who like simplicity.

Sweet they accepted it! i can't remember, was that moon always there or did you add that in?