“She’s not cautious,” Ghislaine Viñas reports, approvingly, of her repeat­ client and close friend Paige West, owner of the New York contemporary-art gallery Mixed Greens. “She’s a superconfident girl-next-door.” At West’s family’s home, the top four levels of a six-story structure that radically reinvented a crumbling 1915 warehouse, her confidence comes through loud and clear. The spectacular 8,000-square-foot space by Ghislaine Viñas Interior Design spirals delightfully into conceptual complexity, sometimes even spirited contradictions—and that goes for the three bathrooms­ and two half baths­, too.

The master bathroom’s glittering glass mosaic­ floor tiles are backed with highly reflective aluminum leaf. For the ceiling, Viñas asked an artist friend, Malcolm Hill, to paint a 1970’s-inspired mural with soft petal and amoeba shapes. “Just in case anybody thought we were taking the bathroom seriously,” she jokes, going on to describe the pair of off-the-shelf mirrors with white-lacquered rococo frames as “frilly and fancy, delicious and disgusting—in a good way.” It turns out that, in context, over-the-top historical elements can appeal to contemporary tastes. Beneath the mirrors stand two Italian bombé chests converted into vanities, each topped with a Carrara marble slab and fitted with an under-mounted sink.

Large white rectangular wall tiles, installed up to the 42-inch-mark, lie flush with the plasterboard above. There’s just a ¼-inch reveal dividing the two zones, aside from over the tub, where Viñas added a narrow shelf and propped a few pieces of art on it. One is a nontraditional portrait of West: The artist simply painted the words “really and truly long blond hair and almond shaped quite light sky blue eyes” in black on a white background.

With daylight for mid-block town houses mostly limited to windows in the front and rear, many of the bathrooms got dark core locations. Viñas compensated by supplying evocations of nature, albeit highly synthesized ones. In the bathroom shared by West’s three young sons, oversize floor tiles are glazed to realistically reproduce photographs of a lush green lawn. “We were having fun with the idea that we live in a concrete jungle,” she says. The ironic grass perfectly complements Arne Jacobsen fittings in a retro shade of kelly green.

Viñas chose the waterless urinals less for their nature-friendliness than for their raindrop shape, a sculptural presence. “I never thought I would say that about a urinal,” she admits with a laugh. Curves continue with the sinks and the radiused corners of mirrors that appear to hover just proud of a wall, thanks to hidden wood blocking. White neon cloud shapes, floating cartoonlike in the air, echo the curved profile of the Sieger Design tub below. “We kept on adding elements of whimsy and fun,” she continues. The clouds are just one example of the distinctive fixtures that personalize each bathroom.

A cluster of fixtures made from ceramic castings of vintage flashlights is suspended in a powder room. In another, black drum shades drip cut-crystal drops. To sell this glam look, Viñas used a line guaranteed to win client approval. West makes no bones about her weakness for sparkle, which Viñas supplied wherever possible. “You’re going to love this,” she’d say. “It’s like diamonds, baby.” Dia­monds­ and a best friend. Could a girl ask for more?