I'll bite. For my wife, I went the vintage style band with a nice solitaire. We are not flashy people and didn't like the over the top triple diamond rings, but at the same time, a straight up boring solitaire is rarely on a woman's list. So, a nice vintage white gold band with a nice quality solitaire diamond was perfect.
Something vaguely along this...
but not quite...
Tiffany style (square) rings I think are nice and ladies seem to like them too!
but in the end... it's her personality and style that will dictate it!