Well nobody submitted a correct answer for the Spot The World Chess Champions picture quiz so Stuart won't have to put his hand in his pocket for anybody's Life Membership !!
The answer to which two of the people depicted in the painting have NOT won the World Championship is :
a) 2nd from left standing - Serkan Ergun, the artist, who for all I know may not even play chess.
b) 4th from left standing - Susan Polgar, who has won the Women's World Championship but not the actual World Championship.
The full list of people in the painting is :
Seated: Kasparov, Spassky, Alekhine, Karpov, Botvinnik and Lasker.
Standing: Kramnik, Ergün (the artist), Capablanca, Polgar, Smyslov, Steinitz, Fischer, Anand, Petrosian, Tal and Euwe.