Edvard Munch died in 1944. (The Scream)
Pablo Picasso died in 1973. (Blue Nude)
ETA: Even if a painting is not copyrighted, and the two above mostly likely are, museums may also hold copyright for images in their collections, as do some private collectors.
Another edit: Different countries have different copyright after death laws. And apparently Edvard Munch's paintings are in the Public Domain now. Explained here