I don't know if anyone is interested in posters/lobby art, but you might want to check out
www.emovieposter.com. It's the site of Bruce Hershenson which has auctions weekly and he has some great stuff. 3 auctions running right now and there is some vitage Disney stuff and modern stuff too. The newest auction has bunches of Japanese posters. Not sure if any Disney in that mix, but always worth checking out. A silent poster (non-Disney) that was gorgeous just auctioned last night for $700, which is CHEAP. So you might score a bargain there. I did!
I'm hoping to find something vintage Fantasia in there some time.