Board Thread:Support Requests - Designing Your Wiki/@comment-34485394-20200309004527/@comment-9605025-20200309014755

The only way to edit the background of a specific page on a wiki is using CSS (see here).

If you want to make it visible just for yourself on a particular wiki, go to "User:IndonesianPlayz/wikia.css" on that particular wiki and create/edit the page with the appropriate CSS. If you want to make it visible just for yourself on all wikis, place the CSS here instead.

You cannot make such a change across all wikis visible for all users. If you want to make it visible for all users on a particular wiki, you will need to have the CSS added to that wiki's site CSS. Only admins can do this; so if you aren't one, you will need to ask a local admin to do it for you.