Board Thread:Ask the Staff/@comment-5057483-20151104123632/@comment-4224349-20151105214247

Sophiedp wrote: You seem to be missing the background file, making it give a 404 error.

Continuing onto what Sophiedp said, it seems like you (or someone else) were recently deleting some images recently. You may have deleted your background image/logo image, causing for the theme to break. Try and look for anything suspicious in the deletion logs.

Or, you can just contact Wikia.