The woodgrain-01.jpg has been taken from the JiGo 2.1.1 distribution and
later modified.

http://www.joot.com/jigo/

The stone graphics were captured from cgoban1, which creates them
algorithmically in a very pleasant manner, and then enhanced with The
Gimp.  I should just rip the algorithm, but the enhancement step is
difficult to make automatic ;)