Board Thread:Support Requests - Designing Your Wiki/@comment-35084100-20180427040421/@comment-9605025-20180427044939

MediaWiki, or at least Wikia's fork of it, doesn't support in-line use of. I have no idea why but it doesn't. What you can do is give the box a CSS class and then use site CSS to apply the background. However, that will only work if you are able to edit the site's CSS.