Board Thread:Support Requests - Designing Your Wikia/@comment-34167962-20151223003203/@comment-4731443-20151223074749

You will need to use Special:CSS, so ideally this is a tabber that won't be changing much. We'll use a trick to target this specific tabber rather than change the appearance of every tabber on your wiki. We'll do that by wrapping the tabber code into a container with an id we can target. For example: (TABBER CODE)

With this, our custom CSS will apply to that tabber: color: transparent; background: transparent url("http://YOUR-IMAGE-URL") no-repeat scroll center center; }
 * 1) startabber ul.tabbernav li a {

makes the text invisible, so you can type in a tabber title as usual, which may be helpful for people using a screen reader.

If you prefer, you could also have both an image and text with something like the following: color: transparent; padding-left: 25px; background: transparent url("http://static.wikia.nocookie.net/b4a8a524-20eb-470d-9f88-1b3a5084be73/scale-to-width-down/50") no-repeat scroll 5px / 15px; }
 * 1) startabber ul.tabbernav li a {