Unmaintained, as I do not use GNOME currently. If you are willing to maintain this, please reach out to me.
GNOME extension to change wallpaper from providers
git clone https://github.com/Jomik/gnome-wallpaper-changer.git ~/.local/share/gnome-shell/extensions/wallpaper-changer@jomik.org
cd ~/.local/share/gnome-shell/extensions/wallpaper-changer@jomik.org
glib-compile-schemas ./schemas/Relog and you are good to go!
Looks, by default, for wallpapers in ~/wallpapers and applies them at random.
As default SFW General pictures with the ratio 16x9 from wallhaven.cc and applies them to your pictures. It downloads a page of pictures at once and deletes them as they are used.