“There is nothing fussy about iron and blackened steel,” said Mr. Butera. No longer sidelined as the metal for overwrought outdoor furniture or bed frames, the decidedly unflashy material is appearing as simple hardware, bathroom fixtures and even flatware, said British interior designer Martyn Lawrence Bullard. Contemporary designers, such as Jasper Morrison blend it with wood and glass, or sometimes create entire pieces of matte black metal. “Welders are the new rock stars,” enthused New York designer Julia Haney-Montanez.

ROUNDED FURNITURE

“It started with the iPhone,” said New York designer Wesley Moon, who’s noting a curvy trickle-down aesthetic in home décor. English designer Rachel Laxer loves the execution of B&B Italia’s Oskar table: “It’s a racetrack shape, almost a rectangle, with the sexiness of curves.” Radial and bullnose edges soften hard materials like marble, said Glenn Lawson of Lawson Fenning in Los Angeles. Meanwhile, Los Angeles designer Timothy Corrigan asked, “Who doesn’t want to rub their hands along a smooth, rounded piece of marble? Touch is essential to design.”

OLD-WORLD ORNAMENTATION

“People want the traditional and dressy, with a shot of nostalgia, to feel like everything is going to be OK,” said Tobi Fairley, based in Little Rock, Ark. In 2016, look for brocades, tapestries and Georgian and Empire antiques. Fringe, cording and tassels “soften the austerity of modern upholstery,” noted Kirill Istomin, who has offices in Moscow and New York. Expect, too, dramatic drapes. “Rooms without curtains are like a man in a suit without shoes,” said British designer Kathryn M. Ireland.

MEXICAN MIDCENTURY MODERNISM

Mexican designers who practiced in the 1940s, ’50s and ’60s, such as Arturo Pani, Eugenio Escudero and Pepe Mendoza, “cling to the clean lines of [American and European] midcentury modern,” noted Jonathan Savage, a designer in Nashville, “but many of them also place a high importance on mixing materials—wood, metal and stone.” South American designers, including Jorge Zalszupin, are also coming into vogue for “uniquely shaped pieces in exotic rosewood and jacaranda,” said Perry Walter, a designer based in Decatur, Ga.

SCANDINAVIAN FLAT WEAVES

“With elegantly balanced geometric compositions, these rugs are a sophisticated answer to the omnipresent neutrals and sisals,” said Los Angeles designer Madeline Stuart, who is fond of early-20th-century designs from the company Märta Måås-Fjetterström. The somewhat folksy carpets adapt to a variety of contexts. “The restraint of Scandinavian design works with both contemporary and traditional interiors,” noted San Francisco designer Heather Hilliard.

In 2015, copper and rose-gold metals so dominated, they’ll be identified with the year. “You can pretty much date a home based on the metal finishes used,” New York-based interior designer Timothy Brown said. While high-quality pieces may stand the test of time, Barclay Butera, a designer with offices in Los Angeles and Park City, Utah, warned, “The rosy-gold hues can go garish and look cheap in moderately priced pieces.” Others maintain that such shades have no place in décor. Says Los Angeles decorator Lindsay Pennington, “Copper is for pots and pans. Rose gold is for jewelry.”

THE INDUSTRIAL LOOK

Joe Lucas of Lucas Studio in Los Angeles considers “industrial chic” an oxymoron. “Enough of looking like we are living in the garage,” he declared. The style has become a signifier of millennial-coffeehouse design, said Mr. Brown, who maintains a design practice in New York. “I’m all for reduce and reuse, but I would prefer not to drink out of another Mason jar in a barn in Brooklyn.” New York designer Julia Haney-Montanez takes the oversaturation personally: “I have ended friendships with people asking me for Edison lightbulb