Instead of a placemat, use a table runner. Fold a table runner and place the plate on top of it. Then, bunch up the other end to create a unique and elegant look. Table runners, like placemats, come in a variety of color, material, and pattern choices, which gives you more options and can be inexpensive. They work well for a round table because the bunched end can be as big or small as you desire, depending on the diameter of your table.
Find table runners at most department stores, such as TableClothsFactory.com. If you can't find a runner you like at any department store, consider using a bolt of fabric instead from Jo-Ann.