Here is an image from unsplash.com.
I don’t know what image I am showing you though. That’s because the URL
being sourced for the above image is
http://source.unsplash.com/random/1200x600. This tells unsplash to
randomly serve us a
1200x600 image. Try refreshing the page and you’ll see
that it is different each time. Cool!
This is a bit of a novelty, but could be useful on occasion. The Gatsby docs use it to great effect in a tutorial so as to not get caught up with the details of serving a specific image.