I created this, which is a much higher quality version of the similar image linked above. I like this wallpaper and wanted it to be higher quality. I don't know who the original artist is, but I made this remaster. Hope you enjoy!
The true original would be the anime. The wallpaper you based this off of was made using a low quality screencap from the opening of the anime. You'll find stuff like that in our really old posts.