The One with the Boobies - S1-E13
Continuity mistake: We've seen the arrangement of Joey and Chandler's bathroom in two previous episodes (1x3, The One with the Thumb, and 1x12, The One with the Dozen Lasagnas) with the sink opposite the bathroom door. In this episode the sink is relocated and the bath/shower is now opposite the bathroom door, for the rest of the series.
The One with the Boobies - S1-E13
Continuity mistake: After Phoebe tells everyone she broke up with Roger, Monica has her legs crossed and Rachel has them uncrossed. In the next shot, Monica's are now uncrossed and Rachel's are crossed. (00:20:50)
The One with the Boobies - S1-E13
Continuity mistake: When Phoebe's boyfriend is talking about Chandler at the coffee shop, the cookie he is holding jumps from his left to his right hand in an instant between shots. (00:03:20)
The One with the Boobies - S1-E13
Continuity mistake: When Joey finds out that his mother knows about his dad's affair, she tells him she's fine and holds her hands to her chest. In the next shot her hands are outstretched in front of her. (00:17:10)
The One with the Boobies - S1-E13
Continuity mistake: When Phoebe is talking to Roger in Central Perk when she tells him her friends don't like him, her hair tie is half way down her back. When Phoebe tells him she doesn't think he's creepy, her hair tie is just above her shoulder. (00:19:05)
The One with the Boobies - S1-E13
Continuity mistake: When Joey's mom comes to tell him that she knows about the affair, he places the paper bag that she brings on the stove and it falls over. In later shots, it is obvious that the bag is upright. (00:17:05)
The One with the Boobies - S1-E13
Continuity mistake: When Joey's mum explains that every day is like her anniversary, her hands are outstretched. Camera cuts and they are lowered. (00:18:20)
The One with the Boobies - S1-E13
Continuity mistake: The way Rachel is sitting when discussing seeing Chandler naked is constantly changing. (00:07:00)
The One with the Boobies - S1-E13
Continuity mistake: When Joey's dad walks in and sees Ronnie, he shuts the door. However, as they go to leave to a hotel the door is open and Joey shuts it. (00:11:50)
The One with the Boobies - S1-E13
Visible crew/equipment: When Joey's mum pushes the sofa bed away, a crew member can be seen hiding behind the sofa. (00:17:00)
The One with the Boobies - S1-E13
Continuity mistake: When they're all sitting together and having pizza, talking about parents, Rachel has no napkin. When she says: "Just think, in a couple of years we get to turn into them", a bunched up napkin appears beside her on the couch. After Chandler's remark it has disappeared again, then it appears and reappears again between shots. (00:21:10)
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.