Ben Schott's recent column in New York Times shows Eleven Madison's Park's "subtle signals to smooth the experience of its clientele" along with its dining room traffic regulations. It also mentions a photo essay for Life magazine portraying Sherman Billingsley, the owner of once very famous Stork Club, carrying out similar means of communication with his staff. Clockwise from top left, Billingsley is suggesting "No check for this table," "Bring a round of drinks," "Bring a bottle of champagne" and "Not important people" or "Their check is no good." More could be viewed here on Nigtclub Hand Signals: A Primer.

Thanks to Mahir for the suggestion.