@david292950g All add-ons are zip archives. In the case of an animated wallpaper the archive should contain tha actual wallpaper in webm format, a preview image in some supported format, and an ini file telling Opera the name and author of the wallpaper as well as the filenames of the other files.
Hey man! I have to tell that is an incredible work, is really beautifull and I wanted to ask your permission to use it in a mod for opera that I am making, if you accept I would leave the respective credits for you and if you don't accept, that's fine, I'll respect it.