As you can guess, there are different ways that will allow you to add random custom header images to your site.

I'll share with you the easiest two ways: using the theme customizer and using a plugin.

So ...

Let's see the first option ...

Method #1: Adding random header images using the theme customizer

First of all, go to Appearance => Customize to launch your WordPress theme customizer:

Then, you need to click on the "Header" tab to expand it.

Note: the header option can also be labeled as "Header image" or "Header media" depending on your theme.

In my case the header tab reveals additional sub-menu items, so I'll have to choose "Header" => "Header image" ...

And as you can see, at this point I don't have any header images yet:

So let's add some header images ...