I would love to do one for the entire staff, the main issue - is number of pages, does everyone have a photo, and (if at an institution) how quick is the change over . . .
Regarding number of pages - how much real estate do you have on the walls backstage?
Alternatively, if it really is just to help acquaint the Audio department with cast, I would bet a packet is all they need, whatever the number of pages. (In my imaginary world where everyone is clever, the sound guy would cut out individual pics/names, and attach those slips to the mic bag or box used to deliver microphones to dressing rooms. A girl can dream...)
If there is high turnover at the level of running crew and casual staff, why not just try to include all the regulars? Some crew may not be working on *your* show, but all the regional companies I've worked at had a short list of people they hired often, even if those folks weren't regular full-time staff. Of course, if you have frequent heavy turnover in the cast, that's another thing...