Natural light can't be emphasized enough. I just moved to a window-less fluorescent fishbowl shared by three analysts/developers, and I've never had so many headaches.
I hate natural light and windows; give me a windowless room where I can set the temperature, light level, etc. exactly, independent of time of day.
The first thing after "private offices for anyone who wants them" is "24x7 HVAC adjustable as close to individually as possible"; I have a shared office in an invite-only coworking space which I largely don't use because the HVAC shuts off at 6pm and is on again at 9am, with huge windows -- it's barely ok in the evenings/mornings during the week, but unusable on weekends.
Maybe it's not possible if you're sharing a room, but in the past I was in a similar situation with regard to natural light. I turned off the ceiling fluorescents and brought in incandescent desk and floor lamps. It made the room much more comfortable and got rid of my headaches.
The first thing after "private offices for anyone who wants them" is "24x7 HVAC adjustable as close to individually as possible"; I have a shared office in an invite-only coworking space which I largely don't use because the HVAC shuts off at 6pm and is on again at 9am, with huge windows -- it's barely ok in the evenings/mornings during the week, but unusable on weekends.