If you feel as if your office walls are closing in, you may be right. Managers' and professionals' offices are shrinking -- down as much as 21% since the 1990s, according to one survey.

Designers are finding new ways to make small offices seem larger -- and to make a powerful statement. With the right layout, furniture and accessories, it's possible to convey values such as creativity, authority or collaborative openness in even a tiny space.

Jeff Berg doesn't have room for much more than a desk and shelves in the 10-by-10-foot office he occupies as a creativedirector at Olson, a Minneapolis advertising agency. If he meets with more than one co-worker, they sit on the floor. But he still manages to project -- and encourage -- creativity. For his lone guest chair, he chose an orange mid-century plastic rocker. 'It's very hard for people to be anxious in a rocking chair,' he says. A large, glittery disco ball hangs from the ceiling. The message: Working in advertising should be fun, he says. 'It's my way of saying, 'If you come in here, we're going to have a party.''

The private office may get more style scrutiny -- particularly from cubicle-bound colleagues -- as it becomes a rarer prize. Just 32% of employees have private offices, down from 36% in 1997, according to the 2010 survey of 424 office-space managers by the International Facility Management Association, Houston, a professional group. The shrinkage has come as employers cut costs and open up more space for meetings and collaboration. About 63% of middle managers still have private offices, averaging about 120 square feet.

Furniture choices speak louder when there's only room for two or three pieces. Stylish pieces that don't scream 'office' can elevate a look. For instance, a classic Eero Saarinen marble table might serve as a desk, placed in the center of the office to lend spaciousness, with a contemporary credenza in a light wood finish along the wall, suggests Asifa Tirmizi, a principal in the New York architecture and design firm Tirmizi Campbell. Nontraditional pieces that combine different furniture styles and eras work particularly well for a person who wants to be seen as a creative change agent, she notes.

One small-office challenge is hosting colleagues. Down the hall from Mr. Berg at Olson, the worn couch in Dennis Ryan's 8-by-14-foot office invites casual collaboration. Mr. Ryan made room for the couch and two guest chairs by choosing a simple desk. The setup avoids 'creating artificial barriers between people,' says Mr. Ryan, chief creative officer at Olson. Three walls are writable floor-to-ceiling glass, covered with project sketches and goals for clients. Another wall displays jokes and photos to foster 'a sense of play,' he says.

Mr. Ryan has held meetings in his office with as many as five co-workers, 'all fighting for the pen, working on the wall together,' he says. While it feels a little like cramming 'five people in a Prius,' he likes the results. 'The small space actually forces intimacy and collaboration, because there's nowhere to hide.'

More managers are opting for a meeting table, paired with a smaller desk, because of the growing number of brief meetings held deskside. A round table has a collaborative feel; folding models on wheels offer flexibility, says Lori Gee, vice president, applied insight, for Herman Miller, a Holland, Mich., furniture designer. Seating guests on bright ottomans or contemporary reclining chairs communicates 'an egalitarian approach,' says Steve Verbeek, vice president, design and innovation, for Teknion, a Toronto-based design firm.

Status-conscious managers have more difficulty projecting an image of authority in a small office. Traditional status symbols such as bulky mahogany desks and trophy walls are pretty much out of the question. Designers are swapping big, dark furniture for desks and tables on lean, lightweight legs. Small spaces seem larger when work surfaces, walls and other materials are pale to reflect light, with colors confined to an accent wall or side chairs, Ms. Tirmizi says.

When a Washington, D.C., law firm moved associates to 13-by-10-foot offices during a recent office relocation, the firm chose desks made of anigre wood, a rich but lighter-colored wood. Attaching the desk to a 'work wall' of shelves and files in a traditional 'L' shape conveys permanence and stability, says Catherine Heath, director of interior design in Washington, D.C., for HOK, the architecture and interior-design firm that handled the job. A relativelytraditional upholstered wooden guest chair faces the desk.

The glass front wall of each office extends around the front corners, creating a bay-window effect that makes the space feel larger, Ms. Heath says. The back wall is covered in pale yellow, and light from a hiddenfixtureoverhead 'washes down the wall like sunshine,' drawing the eye back. Light has an enlarging effect, and research shows bright areas near walls can draw the eye and make the space appear larger.

Extending the horizontal area of a room has a bigger effect on users' perceptions of spaciousness than extending height, says a 2011 study in the journal Environment and Behavior. Furniture can be arranged to keep horizontal sight lines clear. When shelving is 'layered' beneath desk surfaces to create hiddenstorage space, 'your eye doesn't see all the clutter,' says Vanessa Bradley, advanced applications manager at Steelcase, Grand Rapids, Mich.

A 'huge theme' in furniture design is dual- or triple-purpose furniture, says Robert Arko, creativedirector in San Francisco for Coalesse, a design unit of Steelcase. File cabinets topped with fabric-covered cushions can double as chairs, sliding under a desk or table when they're not in use. Ottomans double as storage bins and stools. Work surfaces adjust from sitting to standingheight so employees can change positions. As offices get smaller, Mr. Arko says, 'the space needs to work harder.'

With space so tight, differences in how men and women choose to use it loom larger. Women tend to like more storage for the bags they carry, such as an upright, wheeled receptacle that can slide under a desk where a trash bin might go, says Steelcase's Ms. Bradley. Stephanie Fanger, a workplace strategist with Goodmans Interior Structures, a Phoenix office furniture dealer, says men devote more space than women to tech gear, adding elaborate wall mounts for multiple computers and tablets. Men also tend to choose massive desk chairs with broad backs, while woman opt for light, airy ergonomic chairs with webbed backs, Ms. Fanger says.

Even small offices are prized by their occupants. A 2013 survey of 2,000 white-collar workers by Gensler, a design and architecture firm, found that employees' satisfaction with their work space has fallen since 2008 because many can't find a quiet place to focus. Despite a sharp increase in office space devoted to teamwork, the time employees spend collaborating has fallen 20% since 2008, while time spent trying to focus is up 13%. The survey links trouble focusing with lower job satisfaction and poorer job performance.