wheels for the cts

Alright, so my mom just got a 06 black cts and the stock wheels have winter tires on them so she wants something for the summer. The car is completely stock and will remain that way besides the wheels. i am looking for your suggestions and what you think will look best for stock ride height. i don't want anything black, or bigger than 20's. Its my mom i'm not trying to make her look hood. haha thanks