Hi, Charliegirl

If I understand you right, you've got a circular driveway and want to do something creative with the center.

If that's the case, what about a tree with wildflowers around it and some split rail fence? Of course, the fence would only work if you've got it elsewhere on your property, but it could be very nice. It would also prevent cars from 'cutting the corners' of your driveway.

...wildflowers in WI -- brown-eyed susans, bergamot, milkweed, etc.

Tall, ornamental grasses (that are billowy like love grass) are along one side of the island in our paved parking area. They are tall enough for drivers to see when backing out. If they hit the grasses, nothing is damaged. The grasses are pretty flexible and since we cut them back every year, there's no harm done if someone really ran them down (hasn't happened). Then, we have a mix of shrubs, and perennials behind the grasses.

How about a nice shade tree with a bench under it. A path to it through a cottage style garden. Maybe a little water feature.