pp. Redecorating a home or room to give it a simpler, less cluttered look.
Other Forms
Storytelling — long a factor in many forms of selling — appears to be gaining as a tactic for getting an edge in the crowded field of residential real estate sales. …

Forget "home staging," where firms swoop in, redecorate, and put some potpourri on the stove to boil. Forget "undecorating" to give prospective buyers a blank slate.
—Clayton Collins, “Every house tells a story,” Christian Science Monitor (Boston, MA), March 31, 2004
You're probably ready for the really hot design trend of 2002: editing.

As in: "This room needs editing. " Editing also is known as "paring down," or, as the new issue of Better Homes and Gardens calls it, "undecorating. " Undecorating is when you take a good, hard look at all of the decorating you've done during the last 10 years and … well, undo it.
—Bill Ervolino, “Un to the task at hand,” The Record (Bergen County, NJ), January 17, 2002
1990 (earliest)
The Mazur home formerly was a sales model, ornately decorated with heavy window treatments, botanical wallpaper prints and a primarily green color scheme.

Because of their streamlined taste in design, they have been "undecorating" since they moved in.
—Pamela Dittmer McKuen, “Growing pains,” Chicago Tribune, November 23, 1990
Undecorating also refers to removing the decorations from a Christmas tree or, more generally, removing decorations put up for a party or celebration. Rodeo fans will be familiar with the "steer undecorating" event, in which a horserider is timed on how quickly he or she can to catch up to a running steer and pull off a ribbon that has been attached to the beast's back.