Does anyone know of any sites that have concept art for character design for any games? Peferably for a 2d game B&W sketches.

ut2003 does. but you cant use the art or base characters from it. its copyrighted by the company that created it.

instead it would be better to find some artists or create your own characters.

if this is just for practice, just to a search on google for concpet art. you will find a wealth of drawing information on the net.