Are you so sick of your default background images?
Enter Unsplash - a service with a huge database of completely free, beautiful photos.
Isn't it surprisingly delightful?! 
Install
npm install -g unsplash-so-fancy
It will automatically change your desktop image every 21600 seconds (6 hours)
To change a desktop image now, run
unsplash-so-fancy
Credit
Inspired by Seph's blog
License
MIT