While I wouldn't have used the IQ score as an example, that it is a normal distribution seems a perfectly reasonable way to do it.
Of course, that distribution is going to different for everyone, since there is a large amount of idiosyncratic valuation in terms of physical beauty.
Which means I would say that everyone's curve is going to have a slightly different standard deviation as well, probably. You've got 5 as average and one standard deviation going out to 3-7, like in the graph and then being wider at the edges, going all the way out to 1-9 to cover 2 SDs. I think some people might have a much tighter one, with one SD going from 4-6, or one similar to yours at the beginning and then a harsher drop off.
I also think you can make an argument that it isn't a normal distribution, but that it might be skewed in one direction or another. (I'd be very curious if anyone's done studies on how people actually classify people in the real world. I'm sure someone has.)