Well, I actually get to contribute something significant...
I was stumbling around IMDb one day and found a film from 1975 called "Night Lunch". It is a film focusing on many bands of the time and I noticed that under the credits, Freddie Mercury was listed (as performer in Queen). I e-mailed Amos Poe (maker of "Night Lunch" about this and asked him about how Queen was featured and (since there was almost no sign of this film on the net) I asked if the film would see some sort of public release one day, and this was his reply:
You're welcome! Yes, DVD's out soon, check www.amospoe.com
in 20 days or so... there's a short 3 minute part w/Queen... best/A
Well, I know 3 minutes is rather short, but the IMDb page says that all footage was filmed in New York. Some rather early Queen footage in New York would be very interesting.
All in all, pretty exciting. There are also many other great bands that are featured in this film. Here's a link to a poster for Night Lunch with all of the bands featured: http://amospoe.com/archives/images/nlposter.jpg
If anything else comes to light, I'll post it.