Pillow number and placement: Go for an odd number, like three or five, rather than more traditional pairs. A few big pillows look cleaner than a jumble of smaller ones, which can seem like "too much punctuation," says T. Keller Donovan, an interior designer in New York City and Miami.
Shape and size: Squares should be 18 to 24 inches across, large enough to showcase a solid color or a pattern. Oblongs are a nice foil, since they're "a little less expected," says Katie Ridder, an interior decorator in New York City.
Fabric: A limited color palette and large geometric prints on smooth, tightly woven fabrics, like cotton and linen, work well in a modern environment. But if you love having lots of colors, take a tip that applies to all settings: "Pull them from a piece of art that's in the room," says Andrew Flesher, an interior designer with Gunkelman Flesher Interior Design, in Minneapolis.
Trim: Most trim is traditional, but if you want to use it, make sure it mirrors the pillow's primary hue to "add interest but retain a solid block of color," says Flesher.
2 of 4Ellen Silverman
If You Want a Traditional Look
Pillow number and placement: Two or four large pillows arranged on either side of a sofa impart a sense of symmetry and order.
Shape and size: The right size depends on how big your sofa is, but for eye-pleasing proportions, try pairing square pillows measuring 20 to 22 inches across with smaller squares or circles.
Fabric: Velvet and silk look great in a classic setting. Layering a variety of textures, patterns, and colors keeps things lively. "Sometimes more is more," says Flesher. To help patterns such as paisleys and florals commingle without looking fussy, Donovan suggests pairing a busy pattern with a simple one, like "a complicated plaid with a large floral that's just two or three colors." A print and a coordinating solid will work, too.
Trim: Save the big trim, like tassel fringe, for larger pillows "to give them more oomph," says Scott Salvator, an interior designer in New York City. Small pillows look best with slim trim, like braid or cord.
3 of 4Ellen Silverman
If You Want an Eclectic Look
Pillow number and placement: An even number of pillows runs counter to the spirit of an eclectic room; three or five create a pleasing asymmetry without cluttering the sofa. You want your pillows to look "as if they just happened to be there," says Ridder. For a casual air, try two pillows in one corner with a third at the opposite end.
Shape and size: Pick similarly sized pillows to tie together a diverse collection. Generally, interior designers prefer a few large pillows―18 to 24 inches across―over a mishmash of smaller ones.
Fabric: Be open but not random. You can have a couple of pillows that match or five pillows in five different fabrics, but make sure there's at least one color in common to give the arrangement some unity.
Trim: Avoid excess; keep trim simple and express yourself more through fabrics. Box pillows, with their square shoulders, can be attractive in an eclectic grouping and look great when edged with braid, says Leigh Anne Nomberg, an interior designer with Bill Ingram Architect, in Birmingham, Alabama.
4 of 4Jose Picayo
Decorator Tips on Picking the Right Throw Pillows for Your Room
Consider size. Standard squares (about 18 inches) nest neatly on sofas with typical dimensions. Oversize pillows (24 inches) create a more casual, loungey feel. If you have a modern sofa with a very low back, consider 16 inches.
Know about fill. A feather-and-down fill has more squish, and it’s also the priciest. Foam and other synthetic fills are stiffer. They hold their shape but look less lush.
Use an odd number of pillows. In design, odd numbers tend to be more artful. Try one, three, or five, depending on the size of your furniture and the look you want (one for a chair, three or five for a standard 88-inch sofa).
Create a mixed “pillowscape.” An easy combo: a matched pair of square solids that contrast with the color of your sofa, one oblong pillow for the center of the couch, and two interesting outliers—patterned, embellished, or oddly shaped—that reference either the color of your upholstery or the color of your solid pillows.
Don’t forget about texture. Tactile contrast—nubby linen against smooth leather or silk upholstery, or shiny pillows on a fuzzy couch—add warmth and offer traction, so pillows don’t slide off seats.
Address the whole room. Think of a living room’s pillows as a family. The pillow on a chair doesn’t have to match the group on the sofa, but if it relates in some way—palette, style—the space feels unified and polished.