To me, this is a perfect "inspiration" shot.
I think she looks great just her way she is (very American, healthy, full of life, it just feels like Summer) but if i was a designer I would immediately start thinking "this would also look great if it had a pintuck detail right here.... or a braiding detail on the strap...or this color/print/pattern might...."
I guess what I'm saying is that the dress here is important and yet complete irrelevant. The value is it makes me start thinking of a thousand different variations. I could totally imagine a designer printing out a shot like this, taking white-out to all the specific design details, keeping the overall silhouette and begin designing Resort 09.
To be honest, I think the more perfect "a look" is, the harder it is to be inspired by because it is difficult to imagine it any other way and on any other person. The ability to look at this shot and not see the dress (I know it sounds weird) is very valuable here.