Of all the MLP wallpapers that you've created, I think this one is by far the most successful. The contract between cool and warm was well thought-out, as they're almost complementary. The brushwork is wild and dynamic, giving her mane and wings almost realistic texture on the edges. I like how her silhouette is cropped, rather than seeing the whole body, so that we get enough information to tell what Luna is. The star texture on her hair could use a few more stars, but all in all, you've created a wonderful composition.