Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
WallpapersEveryday - Gorgeous wallpapers on your desktop in just one click or auto-delivered at chosen time intervals.
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Ruler for Windows - It's a screen ruler for Windows.
Wallpaper Engine - Wallpaper Engine enables you to use live wallpapers on your Windows desktop.
Fondo - Find the most beautiful wallpapers from Unsplash.com