Backdrops - The only wallpapers you'll ever need. Say hello to Backdrops.
Splashy - Breathtaking, auto changing wallpaper app for macOS, Windows, Linux, iOS & Android
Momentum - Agile goal and performance management
Irvue - (previously Unsplash Wallpaper) Gorgeous wallpapers on your Mac.
Flickr - image and video hosting website
Splashify - Beautiful desktop wallpapers for Mac and Windows