Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
DailyWall for Mac - Daily curated wallpapers from Unsplash, Pexels & Pixabay 🌄
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Wallcat - Enjoy a new, beautiful wallpaper, every day.
Wallpaper Engine - Wallpaper Engine enables you to use live wallpapers on your Windows desktop.
Splashy - Breathtaking, auto changing wallpaper app for macOS, Windows, Linux, iOS & Android