Group photos are great. i don't know how this can work with the amount of regulars here, but i'm sure something can be figured out for maximum participation. Here's some of the thoughts:
Has to be in the day.
Maybe should be in front of the Main Satge Coachella sign.
PF has to be front and center.
Time for the picture will be difficult, because who wants to be in a picture when they could be watching (fill in artists here)? Friday might be a bad day because not all would be settled. So either Saturday or Sunday afternoon in front of the MS sign?