Board Thread:Support Requests - Designing Your Wiki/@comment-2177054-20131109141154/@comment-5007040-20131109141339

You can use Special:ThemeDesigner on your wiki, but you can only change the background if you have admin rights there. If you don't have rights there it's maybe an option to ask an admin there to upload a new background.

It's also possible to have a background only for you. You can do this through adding codes to personal pages.

Hope this helps you!