Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
Planet Explorer - Interactive global satellite images
Wallcat - Enjoy a new, beautiful wallpaper, every day.
himawari.js - Real-time images of Earth from the Himawari-8 satellite
Splashy - Breathtaking, auto changing wallpaper app for macOS, Windows, Linux, iOS & Android
GlobalXplorer - Become a space archaeologist