As for the customs people have made...
There's the archive of submissions to Quinn's column at the Palisades Club subsite.
There's an archive of some of Quinn's own stuff at
www.toymania.com I think, someone posted the link a while back.
MrTheFrog has his own site with his custom sculptures, and I believe WiGgY started a site to host other people's customs.
But I'm not sure if that'd cover the totallity of all the custom Muppet figures people have made and shown there at the Palisades boards. Hope this helps.