NEW YORK — Contemporary firm Bisou-Bisou is setting its sights on its customer’s little sister — or daughter, as the case may be. The company’s junior collection, fittingly tagged with a diminutive “b,” is a bit funkier and more playful than its older sibling. Innovative fabrics, for example, play a starring role, with embossing and foil treatments, Ultrasuede and metallic effects among the key looks for fall. Here, b’s nylon and spandex tube top and polyester and Lycra spandex skirt.