Chess_Pieces_Sprite.svg: https://commons.wikimedia.org/wiki/File:Chess_Pieces_Sprite.svg
Single chess pieces, also from wikipedia:
https://upload.wikimedia.org/wikipedia/commons/f/f0/Chess_kdt45.svg https://upload.wikimedia.org/wikipedia/commons/4/47/Chess_qdt45.svg https://upload.wikimedia.org/wikipedia/commons/f/ff/Chess_rdt45.svg https://upload.wikimedia.org/wikipedia/commons/9/98/Chess_bdt45.svg https://upload.wikimedia.org/wikipedia/commons/e/ef/Chess_ndt45.svg https://upload.wikimedia.org/wikipedia/commons/c/c7/Chess_pdt45.svg
https://upload.wikimedia.org/wikipedia/commons/4/42/Chess_klt45.svg https://upload.wikimedia.org/wikipedia/commons/1/15/Chess_qlt45.svg https://upload.wikimedia.org/wikipedia/commons/7/72/Chess_rlt45.svg https://upload.wikimedia.org/wikipedia/commons/b/b1/Chess_blt45.svg https://upload.wikimedia.org/wikipedia/commons/7/70/Chess_nlt45.svg https://upload.wikimedia.org/wikipedia/commons/4/45/Chess_plt45.svg