The One With Ross's Wedding, part 2 - S4-E24
Continuity mistake: When Phoebe is on the phone to Emily's mum she is making a sandwich. We see her put mayonnaise on it, the shot flicks to Emily's mum then comes back to Phoebe and the mayonnaise is now gone. (00:26:45)
The One With Ross's Wedding, part 2 - S4-E24
Continuity mistake: In the scene where Monica and Ross discuss how Emily has decided to call off the wedding after Monica suggests they postpone the wedding, Monica is wearing a black watch on her left wrist. This disappears and re-appears a number of times throughout the scene. (00:15:00)
The One With Ross's Wedding, part 2 - S4-E24
Continuity mistake: When Felicity finds Joey outside the wedding venue she closes the door. But when they start kissing, the door is completely open. (00:35:50)
The One With Ross's Wedding, part 2 - S4-E24
Continuity mistake: As Ross says, "This is our wedding day," in a close-up, Elliott Gould is holding a bit of paper in his left hand (glasses in his other hand, out of shot). In the wide shot, the paper is in his right hand, then jumps back to his left when the angle changes. (00:36:25)
The One With Ross's Wedding, part 2 - S4-E24
Continuity mistake: Joey is in their hotel room asking Chandler where Monica is, and the open bathroom door behind Chandler alternates from wide open to halfway open between shots.
The One With Ross's Wedding, part 2 - S4-E24
Continuity mistake: In the episode where Rachel goes to tell Ross she loves him (in England) she leaves her room with a brown sleeveless vest and a cardigan over her shoulders. The cardigan then disappears in all other shots until after Phoebe says "he's in love with the British chippy". Her leather jacket also goes from being in her hands to over her arm. (00:19:30)
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.