Board Thread:Support Requests - Designing Your Wikia/@comment-25616959-20150817180143/@comment-4731443-20150819173615

NeoAxL wrote: I tested adding the "background-dynamic" class to the body tag with Firebug and it did work! Though I am not sure how do I force the class into the the real Wiki CSS.. As far as I know (I'm no expert with CSS), you won't be able to just add the class to the actual body. However, using custom CSS (at Special:CSS), you could copy and paste the class's effects into the rules for the default body element so it would behave the same. However:
 * 1) You'll have to make sure you don't forget anything. For example, different rules get implemented based on screen resolution (no background displayed under 1066-px IIRC, and different spacing for wide and very-wide screens), so you would have to include all of them.
 * 2) Wikia does not recommend using custom CSS for things that can be done with the Theme Designer and affect the entire site because the global CSS changes from time to time and could break compatibility with your homemade style. That's why I don't recommend doing this although it looks like a possible solution if the staff can't solve your problem.