All those women look lovely - the women in the white bikini and green bikini bottoms have especially nice figures.
Like most people have said, it depends entirely on height. I think your body frame carries some weight (haha) too in deciding whether you can be bigger or smaller.
Course, a tall, say 5'10" girl can be a bigger size ie. a 12 and look as thin as a small, say 5ft girl who is a size 6.
But frame also has to be taken into account. I'm 5"1 and a size 6 and if I get any bigger than an 8, I start to look chubby and weird becausw my frame just looks bad with extra weight. My best friend on the other hand, only a smidgen taller at 5'2" is a size 12/10, really busty, looks amazing because her frame is slighter larger despite being small.
I think the general gist is, s'long as you don't have multiple rolls of fat upon your person, you're good to go whatever size.