The pictures aren't really anything special.
The issue is that they were taken behind the construction walls by somebody who shouldn't be there or by somebody who shouldn't be taking them. So either it's trespassing or going against an NDA.
Because of that, I don't know if you can call the photos illegal but Universal sure as hell don't want them out there and having them on this forum either linked or hosted is a big no no. It makes the website owners liable and given the website requires a working relationship with Universal to work, it's just not worth the risk or the hassle.