Let me show you this little Python script I wrote today. It automatically downloads the most recent Astronomy Picture of the Day from nasa.gov and sets it as your desktop wallpaper. I really like these pictures as they are always of great quality.

change_wallpaper.py on gist.github.com

To install it, just download the two files from the above link and edit them accordingly.

Image of 2014-06-19, Credit & Copyright: Luc Perrot