Paris nude models went on strike yesterday. Paris City Hall wants to strip art school models of the tips they receive from painters and sculptors _ and the nude models decided they weren't going to take that with their clothes on. About 15 models braved near-freezing temperatures to strip outside the city's cultural affairs bureau Monday to protest a new municipal order that again bans the age-old practice of tipping those who pose nude. The tradition goes back a long time, since artists like Modigliani and Picasso used nude models. Most work part-time, earning a similar wage to a housekeeper, but those with unique body types may work full-time.