5. Make open spaces feel intimate.

Jonathan gave the dining room, a recessed nook just off the living space, a cozy vibe with a subdued palette of grays and whites. He shielded the quieter spot from the lively great room with an architectural screen affixed with two back-to-back Philippe Starck mirrors. "A screen is a great way to create instant architecture," Jonathan says. "We chose one that's modern but a little bit decorative, to match the style of the building."