Very good wallpaper! I like the splash and droplet effects used here; they are very well done. The use of negative space is also superb and makes for a nice accent. I particularly like the way that you used similar colors to your subjects in the background, but you blurred the background enough to make it feel different. This makes them feel related, yet it avoids monotony. You further distanced your subjects and background using the semi-transparent graphic, which I thought was an excellent call as it adds some depth and interest.
Finally, when it comes to the content, I thought that your touching upon the idea of "Conscience" was well stated for a wallpaper. You used two different sides of the same pony, the good and bad sides, and connected Vinyl to her good side using more of the splash effects. To me, this signifies that she is choosing that side of herself and rejecting her darker side. Very interesting.
The only thing that I would have done differently (and it is a minor qualm) would have been to add some more texture to the background to add visual interest and increase the depth of field. Other than that, it is an excellent wallpaper!
Favorited! P.S. Sorry for the random critique mode... I don't know what came over me.