Sketch This - Daily drawing challenges
Wallcat - Enjoy a new, beautiful wallpaper, every day.
ChalkMotion - Create animated doodle slideshows
Splashy - Breathtaking, auto changing wallpaper app for macOS, Windows, Linux, iOS & Android
Cycloid Drawing Machine - A mesmerising spirograph-like web app
Irvue - (previously Unsplash Wallpaper) Gorgeous wallpapers on your Mac.