Ralph designed quite a lot of stuff for the special.
http://www.ralphmcquarrie.com/gallery_1/star_wars/tv_special/index.html
The $64,000 question about the Holiday Special that may never be answered is: Why didn't George take advantage of that recreated Cantina set (not to mention having Harrison Ford handy) and reshoot that Greedo scene he was so damn unhappy with? ;)