Oh boy, this is a dangerous topic for me.
I love me some wallpapers, and even before it was a feature in Windows I got a program that would auto-cycle them for me, NuonSoft Wallpaper Cycler. I still use it because it's a little more robust than what Windows 10 will do for you. I've got something like 1,000 wallpapers and it's set to switch on 80 minute intervals.
My favorites tend to be anime walls, the really artistic ones. Many I got from a site called AnimePaper.net, but it shut down quite some time ago, maybe eight or ten years.
But since this topic just got bumped (didn't notice it originally), I'm going to inflict a few of my old faves upon you all. Hopefully someone will enjoy them.