Custom Header images

Hi there

I've a quick question. At the moment the image location on a custom page header looks like it's centre centre. Unfortunately the person I'm creating a site for has some photos of people to put into the headers where their heads are near the top of the image.

I know I can use CSS to target a particular page and change the location of the header background-position from center center to center top, but ideally I'd like to target a particular header, call it header-portrait or something, and just let them choose it from a list.

Is this possible at all?

cheers

Jason