Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Splashy - Breathtaking, auto changing wallpaper app for macOS, Windows, Linux, iOS & Android
Wallcat - Enjoy a new, beautiful wallpaper, every day.
Irvue - (previously Unsplash Wallpaper) Gorgeous wallpapers on your Mac.
WLPPR - Beautiful mobile wallpapers made from satellite imagery