Zina Saunders has interviewed and painted various communities of New Yorkers. It started with Puerto Rican Bike Men and continues with numerous other groups, including Bike Messengers.
Disc brake, Aerospoke, Xtra-Cycle (just wha!?) on this last one; the base frame design looks real cheap, though!
Those three are my favorites. View the rest of them at Overlooked New York.