1.
Found during a board game: Martin Johnson Heade
2.
Found in a Wisconsin living room: Van Gogh
3.
Found in rubble by a peasant: the Venus de Milo
4.
Found at UC Berkeley, then promptly undersold: Sargent Johnson
5.
Found in a garage sale: Andy Warhol
6.
Found in a basement: Picasso
7.
Found in a thrift store: another Picasso
8.
Found in a thrift store: Jackson Pollock?
9.
Found in a thrift store: Ilya Bolotowsky
10.
Found in a couch: Venetian painting
11.
Found in walls: Mayan murals
12.
Found in walls: a Dada mural
13.
Found by accident on the internet: Thomas Kinkade's "Disney Dreams Collection"