MadMonkey: There are zillions of freely distributable games that include Mah-Jong based games. I'd be surprised if none of them had a license that forbid using just the graphics.

For instance, the fanclub version of pysol includes Mah-Jong graphics, which are distributed under the GNU license. This means that Fencer can freely use them - the license would only mandate Fencer to do something if he was going to distribute the code of BK.