Add a touch of coral. Coral is an excellent foil for green and black, and it will soften the boldness of the two colors. A coral bowl is practical yet artistic, or choose a sculpture or other free-standing work of art that features coral as its primary color. Alternately, spray paint something coral -- such as an old birdcage.
Place a rug under the coffee table to anchor the space. The rug should feature most or all of the colors in its design.
Set out some books. Coffee table books, of course, are ubiquitous on coffee tables, or try something different instead. A stack of timeless literature is sophisticated -- remove the dust jackets for a classic look. Or, fill a basket with your favorite novels.
Bring in the color of the couch to add a cohesive look to the arrangement. Fill the coral bowl with green apples, or arrange some green fat, tapered candles on the table. A green plant will also tie the group together. If you want to lighten the look a bit, add touches of white by using white candles and a white basket to hold the books, plant or coasters and your TV's remote control.