IT WAS not love at first sight for Amy Studebaker and her family's would-be St. Louis house. Rather, it was pure weariness and nagging potential that won her over.

"We spent about a year looking at homes," says the decorator. "We probably toured over 100." None of them felt right. Finally, exhausted by the endless search, she and her husband, Nick, revisited a 1950s brick Colonial with easy backyard access to a beautiful park. "I remember saying, 'Let's just buy it, and I can do something with it,' she remembers."

They altered the irksome elements—opening up some spaces and closing off others—and added a Louisiana-inspired balcony and columns to the exterior to deliver what she calls a "more Southern" first impression. They then highlighted its existing charms, like the original plaster walls and crown molding. "It had those historic details that I find to be really important, which make for a sturdy house," says Studebaker.

In the six years they've lived there, the designer has updated the once lackluster place with character-building moves, energizing rooms with spectacular wallpapers, reimagining furnishings with pretty upholstery, and layering on antique and vintage finds wherever she can squeeze them in. Her creative spark shimmers brightly at Christmastime, when she trims every inch of the house with velvet ribbon and natural greenery. "I love the holidays," says Studebaker. "We spend a lot of time with our family and friends, so there's this warm, cozy sort of feeling, which I like to bring into our home through the decorations as well."