Muzei - Muzei is a live wallpaper that gently refreshes your home screen each day with famous works of art.
Irvue - (previously Unsplash Wallpaper) Gorgeous wallpapers on your Mac.
Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
Unsplash Wallpapers for Mac (Official) - Curated, HD desktop background photos from Unsplash.
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Unsplash - Unsplash is a website with high-quality free HD images. It has a catalog of more than three hundred thousand striking images that are neatly organized with tags. Read more about Unsplash.