I've started doing some research on the business side of art freelancing.
Generally I feel that there is little of conversation among the artists about the fees. This probably is due to the saying that gentlemen don't talk about money." However, sometimes it's hard to pinpoint the fair fees, because of different "sizes" of clients.
I want to keep my findings over here, along, with my sketches.
http://mariabrophy.com/art-licensing/what-to-charge-for-art-licensing-royalties-advances-and-flat-fees.html
http://mariabrophy.com/business-of-art/artists-beware-of-these-red-flags-in-licensing-contracts.html