How about breaking it up into tasks? One person volunteers to co-ordinate photos of all of the teams from a regional. They delegate people (maybe including themself) to photograph each robot in the pits. Another set of delegates (probably with media passes) photographs all of the teams from the regional at field level. Repeat everywhere.
Make sure to take high-quality colour images when possible—but none of that film stuff, unless the photographer also volunteers to scan the images in a timely fashion.
Then upload the image files to a central repository. (Maybe The Blue Alliance, maybe FIRSTWiki, maybe even Wikimedia Commons. Either way, be sure to list author information, date and location, plus some information about the image. And photographers need to explicitly release their images under some licence—this saves so many headaches later on, e.g. if FIRST wants to use your photo in a brochure, they know how to credit you. I strongly recommend
CC-BY-SA 3.0.)