Josette Simon

My choice to play Nina Simone would be Josette Simon http://www.imdb.com/name/nm0800219/

No pictures on IMDB, but there's a good picture of Josette here:-
http://www.naxosaudiobooks.com/northamerica/josettesimon.htm
But you can google for more.

I've no idea what she sounds like singing, but then no-one will sound like Nina, and a musician will have their own sound, so why not get a good ACTOR and go from there?