The first story I wrote in what turned out to be a silly series called Conversations with the Grand Fiend came from a art prompt. I don't use museum art prompts, I have a bunch of original cartoon art at home and this was one of them and I started the piece with just this cartoon to go on and the story just happened while my son watched Backyardigans in the next room

Here is the illustration, but Scott Nickel, who does nice things
http://www.gocomics.com/eek/2008/02/26

Here is the story
http://www.linguisticerosion.com/2012/05/conversations-with-grand-fiend-issues.html