I'm guessing legal concerns. Hey, bringing happiness and excitement via actual close-up photographs isn't easy- we're lucky to have gotten the glimpse that we did. Even though the press for the site is very cool, I have a good feeling that Disney isn't too happy about pictures being released that they didn't release-for a ride that they haven't released too much info about!
(Also, everyone ought to do their cut and paste now and try to help avoid any legal hogwash regarding the great pictures to help preserve the integrity of our beloved site- no offense, but posting copies might be a little sketchy if "we" are trying to stay in the clear.)