A Solid Choice is Solitaire
The round cut diamond is versatile, so it complements many different settings, and because of its popularity, many settings are designed with a round diamond in mind. Because of its brilliance, the round shape is often featured as a solitaire diamond in a simple setting. This allows the focus to be on the main diamond, and is a classic, chic choice.
If you want to add a little sparkle to a solitaire style without going overboard, then consider adding a few smaller diamonds to the band. Diamonds that are inset into the band will add a bit more twinkle without distracting from the beauty of the center stone.