Someone has suggested Gericault’s Raft of the Medusa (1818-19) for a flash mob. It’s a great painting with lots of drama, politics, suffering, a happy ending for some, and a cliff-hanger. And it’s a BIG painting: 16″ 1″ x 23′ 6″.
I generally don’t send students to Wikipedia, but this link is an excellent short account of the work.
Here’s another great work of art flash mob: