Waiting for the next band to play at a concert is simply dreadful. You either go get more beer, talk about the previous band, talk about the band that's coming up or eavesdrop others talk about the previous band and the band that's coming up.
I do not know why there are such a lack of activities in between the changeover of bands at a concert. Here you have the perfect opportunity to entertain the restless crowd and anything you do, music related or not, will be appreciated. This is pretty much a marketer's dream playground, a place to pillage and plunder as the crowd are at their most vulnerable but receptive best.
Like promoting a new band from the same label/concert promoter, show music videos, screen movie trailers, play XFM, get someone to do standup, do a contest... anything. Anything is better than listening to a couple of 16 year olds rambling about Johnny Borrell and Kirsten Dunst.