Mitchell,
Great question. It’s probably been about four years since I last worked with WP E-commerce so my experience level is pretty low. It does predate custom post types, so I’m not sure how the content is stored in the database or retrieved. To try a custom solution, we’d have to know that for sure.
One way to mimic that style would be to use an image gallery. It’s possible to link the individual images to any URL. You could create a gallery, place a thumbnail for each of the products you’d like to display and then link them using the URL option. That would give you a grid display of products and not require any custom coding.
It’s just a though, but that’s probably the simplest way to go about it.
If I can help, just let me know,
Bill