I'll name something with an amazing fanbase: Touhou. Touhou is like 10% canon, and about 90% fanbase. Heck, Touhou's simply a video game series, yet it has an anime series in the works (WHICH IS ALL FAN-BASED). It has several animated videos on Youtube and other various places, and it has fanart (some which is slightly pornographic, but Rule 34).
In fact, the fanbase and the canon are so tightly intertwined that sometimes ZUN (creator of the Touhou games) incorporates elements from the fanbase.