Change primary image...

Here's the scenario.

I'm working on this site:
s446956729.onlinehome.us/

The images on the home page are featured from Hikashop, obviously. They're nice and lovely portrait photos. All fantastic.

Now my client wants landscape images on the homepage instead of portrait images.

My question is, is there a way to easily set the primary image of a product, so that it's the first one picked when featuring a group of products on the home page?

Or is there an easier, better way of doing this?