Cosmetic dentist Dr. Huefner has a good post about how to select porcelain veneers to suit your face. Above are two of five examples. The first image shows a more masculine smile. It suits an older face, it is square and flat. The second shape is called the "Enhanced” smile style, and is apparently popular with many beauty pageant contestants. See that the second teeth from the center are a little shorter than the front teeth. This gives a youthful effect dentists call “the gull wing” and is attractive on many females.

See three more popular veneer shapes here.