@Iluviaporos - I'm particularly fond of inference in art, although most of the examples I can think of off the top of my head are ones I've seen in picture books, rather than ones I've seen in paintings.
When you've got text to go along with the pictures, you can play them off each other so that a different story is told to the one that might exist if there was only one component to the narrative.
I guess a very basic example (in terms of narrative, at least) is that famous painting of a pipe, which has the words underneath it (in French) "This is Not a Pipe."
If you had either the words or the image without the other, there would be no story. But because they are both there together, the audience has to infer more meaning than they might have, otherwise.