On your Jekyll layout, load the Backstretch plug-in.
Add this to your Jekyll layout after the script tag that loads the Backstretch plug-in. This will select a random image and display it. Like so:
Note: Be sure to replace the image file names and path with your own.
Use the Bootstrap jumbotron class to display the background image on your page or post and you’re done!
If you want to have the flexibility to override the random image with a specific one determined on a page by page basis, you can just add a few modifications:
In your page’s front matter, add a variable with the image name, like so:
That’s it. Load and reload your page and you should see the image changing randomly.