Random masthead image

Yup.
https://weblogtoolscollection.com/archives/2004/04/17/random-image-header/
There’s something similar at alistapart too.

I don’t get it….how does this work?

Where should I put it?
How should I upload it?

Read the file that comes with it and the instructions on the page. You put it where you want it, I assume in the header.php file. You have to put your pictures in a folder it can find…it’s all spelled out on the web page.

There are also instructions by the developer here: https://photomatt.net/scripts/randomimage

You want THIS: https://www.redalt.com/Tools/kubrickr.php

Why?

Doesn’t that just change the kubrick image? Does it also produce random images?