The One Where Monica Sings - S9-E13
Continuity mistake: When Rachel is talking to Gavin at Ross', her position when she's sitting changes depending on the angle. (00:14:20)
The One Where Monica Sings - S9-E13
Visible crew/equipment: When Gavin goes to the door to bring Rachel soup you can see a camera man's microphone in the top of the screen. (00:10:50)
The One Where Monica Sings - S9-E13
Visible crew/equipment: After Joey dips his finger into the hot wax and smears it all over his hands, when Sonya walks out of the back room we can see her tape mark on the floor, which she promptly steps on.
The One Where Monica Sings - S9-E13
Continuity mistake: When Phoebe, Monica and Rachel are talking in the coffee house, a waitress walks by and in the next shot when the camera focuses on Monica, and comes back to Rachel, the waitress walks by again. (00:05:00)
The One Where Monica Sings - S9-E13
Revealing mistake: When Joey has his eyebrows plucked at the salon, it is obvious that the woman is not pulling any hair off. (00:07:00)
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.