Pharrell Williams continues trying out new careers, designing another piece of furniture for Galerie Emmanuel Perrotin. Following last year’s “Perspective,” a chair resting on a man and woman’s legs in a unsubtle homage to sex, comes “The Tank.” Riding on plexiglass treads, the leather seat, upholstered in blue, black, white or pink, will be unveiled at Art Basel Miami next week to help generate some hype.