Item Image / Featured Image

Hi there. I have just taken over a website that is using your plugin. I would like to change this to work with a different template. However, when I use the catalog with the template I would like to use the item image does not display in the catalog. If the item image was actually the featured image for the post then it would work, but it seems the item image is not the featured post image. How can I make the item image display as a featured image so that it will display in any post type?

The page I need help with: [log in to see the link]