Set down a rug with a pattern that includes the colors of your mismatched pieces. Braided wool rugs, Oriental patterns and floral designs have a wide range of colors that are likely to include those you are trying to match.
Arrange matching toss pillows on your couches. Choose pillows with patterns that include the colors of the couches to bring a sense of harmony to the room.
Hang window coverings--shutters, blinds or curtains--in neutral colors, such as white, cream or tan.
Frame artwork in matching picture frames. Choose a simple frame that is not much larger than your picture.
Display similar collectibles throughout the room to bring cohesiveness. Whatever you love to collect can be used to bring the room together, whether it's a collection of china dogs, baskets, primitive dolls or nautical items.
Cover the couches with matching slipcovers, if you cannot stand the mismatched look. Slipcovers are available in a wide variety of colors and patterns.
Paint wooden furniture the same color to create a matching look. Painting furniture white and lightly scuffing the finish is a shabby chic look that brings mismatched pieces together.