One idea is to use a circular ottoman. Bonus points if you opt for a storage ottoman. Wayfair has some good ones, and Bassett Furniture has a custom design program for theirs, which are really inexpensive. If you have a little money to spend, you can add a trim, like fringe, to bring more flair to the base. If you aren’t into the round shape, go for a more organic element. I love cowhide rugs. They have a natural shape that adds movement to any room. You can find them at Ikea. If you don’t like the notion of a real animal skin, there are tons of faux hide vendors on Etsy. Use the skin just as you would an area rug, under a coffee table or on its own.
Curved sofas can give balance to a rectangular space. They function like standalone sculptural objects, which add fluidity and sexiness to a room. My favorite is Vladimir Kagan’s Sloane sofa. I like to position a pair of them facing each other to define a discrete space. They invite conversation in ways a straight sofa doesn’t. For a low-cost alternative, take a cue from my showroom in the Merchandise Mart. There, we’ve hidden the edges of a floating wall with floor-to-ceiling circles cut from Phillip Jeffries wood wallcoverings.