The One Where Rachel is Late - S8-E22
Visible crew/equipment: After Rachel has told Ross it's 100° outside and she starts walking towards the door, a camera is visible to the far right (Widescreen version only). (00:09:30)
The One With Rachel's Date - S8-E5
Visible crew/equipment: When Rachel and Cash leave Joey's apartment, in the top-left corner a stage light is visible. (00:12:05)
The One With Rachel's Date - S8-E5
Visible crew/equipment: When Phoebe is telling Monica about Tim, there is someone in the background with a black mug that is reflecting some of the stage lights. (00:05:20)
The One Where Rachel Has a Baby, part 2 - S8-E24
Visible crew/equipment: After Rachel asks Joey to get the other box of tissues under Ross' coat, when Joey drops the ring box then picks it up and opens it we can see the end of the hospital set floor and wall, behind the chair.
The One Where Rachel Tells... - S8-E3
Visible crew/equipment: When Monica is yelling at the other couple on their honeymoon, the things on the shelves behind them shows the reflections of set lights. (00:15:25)
The One With The Red Sweater - S8-E2
Visible crew/equipment: When Joey walks into Monica's apartment and Monica screams "I don't know how any of these got open" while throwing a box, a lot of stage lights and a boom-mic are visible above Joey's head. (00:17:00)
The One Where Rachel Has a Baby, part 2 - S8-E24
Visible crew/equipment: In the very last shot of the episode, as Ross is walking down the hall, stage lights are visible at the end of the hallway.
The One Where Rachel Has a Baby, part 1 - S8-E23
Visible crew/equipment: Right after Rachel says, "Do you know that feeling when you're trying to blow a Saint Bernard out your ass?" the camera cuts to a view of Monica and Chandler. Behind Monica and Chandler, part of the set is visible, along with a man on crutches.
The One With The Secret Closet - S8-E14
Visible crew/equipment: When Chandler walk in Joey's apartment and say "Rachel's all moved out, huh?" as he walks towards Joey a lot of set lights are visible above their heads. (00:18:55)
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.