Let's say a company makes video games and unauthorised fanart of one of the game's characters is made and posted on the internet. The company finds this fanart and uses it in merchandising etc.
Who is liable to whom and to what extent?
Could the fanart author sue the company for use of his work? If they countersued for his creation and distribution of the unauthorised work what would the "net" effect in terms of liability be?
As secondary questions how would trademarking of the original character design affect liability?