I'm not entirely sure how it works myself.
But from what I can gather, the formats
you can use are GIF, Video, Scenes (in-engine built), and WebGL (or HTML5).
It might just be as easy as some editing the unity project for auto-play and exporting it as WebGL.
The only downside is lewd stuff is against ToS for Wallpaper Engine, so a few things would have to be SFW'd (nothing said against innuendo ;) ).
example of functioning WebGL: https://steamcommunity.com/sharedfiles/filedetails/?id=1116014641