la peinture ~ PRON: lah peh-n-chur is a generic word for painting. It can be used for any painting on any media/surface. Une peinture could be anything painted, including a fresco.
un tableau ~ PRON: uhn tab-LOH specifically refers to a work on a canvas (or similarly portable media) that you could hang on a wall.
Que pensez-vous de ce tableau autoportrait de Van Gogh ?
