I didn't see anything on the forum rules in terms of pictures and videos violating anything. Most likely pictures that are sold on eBay or Amazon would be copied quality pictures which by the seller is unknown if it's authorized or not or an original print. Personally I think it's okay if a picture link on the forum would be okay, as long as it's not printed out or saved, if it's a link to it's original website, it shoud be okay because links and videos no matter where it's posted, it's attacted to it's original link so it should all be legal. And besides that, since it is eBay, if the auction has ended, the image link probably wouldn't last long anyways.
But aside from all the legal mombo jumbo discussion, back to the main focus of the picture. I never knew that Muppets Inc. did something with the Dental Health Association. Though I'm not quite sure if the girls in there are in fact Lisa and Cheryl. Sometimes in projects Jim's kids would be a part of it and sometimes they won't, especially in commercials like the Easy Bake Oven with Little Bird for instance.