The One With Frank Jr. - S3-E5
Stupidity: The friends discover that Joey's built a ridiculously oversized entertainment center only after they've pushed it upright. Cute concept, but there's no way that's when it would have become obvious. First of all, all they had to do was see it stretched across the doorways when it was lying flat on the floor. Second of all, Chandler had been watching it get built; even if he wasn't really paying attention, it would have been very immediately obvious at a single glance. And Joey's a space cadet, but there's no way he wouldn't have noticed either.
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.