Chess pieces by Colin M.L. Burnett ("Cburnett"),
https://commons.wikimedia.org/wiki/Category:SVG_chess_pieces

Multi-licensed by the author under GFDL, BSD and GPL; used here under the BSD license.
Source files: Chess_{k,q,r,b,n,p}{l,d}t45.svg on Wikimedia Commons, renamed to wK.svg, bK.svg, ...