As usual, Daniel is right. Though I'm not sure unlinking and then linking would work, since the default order is upload date. You'd actually have to unlink the image and then upload another copy. (The first image will automatically be deleted from our system after two weeks of being unlinked.)
FWIW, you can resort _your view_ of the image order at any time. But when you or someone else comes back to the profile the default is always upload date.
We thought about enabling users to set the order manually, but that would be a bit complicated because of the way we allow images to be linked to multiple people.
I suppose it would be relatively easy to change the default sort order. We could have the default be date or popularity.