The One Where Ross Got High - S6-E9
Rachel: You guys, it was bananas, cream, and beef! I just cannot believe that you ate that so that I wouldn't feel bad.
Monica: Actually, I didn't eat mine. It's still in the bathroom.
Joey: No, it isn't. I ate that.
Judy: And we left ours in Monica's bedroom.
Joey: No. Got it, [nods to Jack] and got yours, too.
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.