User blog comment:Harbumz/Introducing Vignette, Wikia's New Thumbnailer/@comment-452-20150212014153/@comment-24880673-20150212045952

It looks like the images used in that template have an extra "/" after "images" and before "thumb" (i.e. "images//thumb") that's causing the problem. The vignette version would be http://vignette.wikia.nocookie.net/messaging/images/thumb/7/79/CC_some_rights_reserved.svg/revision/latest/scale-to-width/90?format=png.