The One With The Proposal, part 1 - S6-E24
Continuity mistake: In the scene where Richard is being seated next to Chandler and Monica, the amount of champagne in Chandler's glass changes. (00:09:20)
The One With The Proposal, part 1 - S6-E24
Continuity mistake: When the waitress opens the door to the kitchen to tell Monica about a complimentary customer, in the first shot the waitress pulls the door open and stands in front of it, but in the next shot she's pushing the swing door into the kitchen poking her head in to talk to Monica. (00:20:35)
The One With The Proposal, part 1 - S6-E24
Continuity mistake: When they are in Central Perk deciding who will go with Rachel to the auction, Rachel's purse and the cups in front of Joey move around. (00:02:20)
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.