Possible Clues:

• "The Last Supper," for one
• Hard-to-move painting
• Public artwork by Lady Pink, e.g
• Chagall piece
• Work by Chagall
• Subway artwork, perhaps
• Fresco, e.g.
• Subway artwork, e.g.
• 'The Last Supper,' e.g.
• P. ain't on the wall