Are you familiar with CSS? Do you want to edit the background of those pages as well? Just trying to get more details to help you out.

@Nikathelostio I'm not familiar with CSS I just want to be able to create customizable pages seen in the links I put in my original post for a different wiki I'm in. I've added two CSS codes that I copied and pasted in the Common.css page.

(code above has nothing to do with the page customization question just showing code copied and pasted)

The first code (the one with <pagename> should be more reliable if it works and it doesn't slow down the page, so try that first.

But it should be /* Custom background */ and not /* Custom background

Otherwise:

From what I can make out, it seems like it's built up like this:

1. The core (a Lua script)

2. The base template that implement the feature to add CSS scripts

3. A theme made as a template

4. The page itself which includes the theme template

Try copy pasting the codes on those pages to your wiki and see if that works. And if it does, you may edit the Pool theme template (rename it even) and create other theme templates like that one, just remember to edit the pages that uses those themes too.