each package has its own discussion forum, so package specific questions like this are normally better suited for there. anyway, you might be best off creating a separate page for each category, each with its own proPhoto instance, like what I'm doing here:
http://inneroptics.net/collections/...
that collection page is just using a custom template with the page list block, and each category subpage has an image/file attribute assigned to it for the category thumbnail.

that's actually what I am doing... it's just that there are so many categories and the client wants to add new ones himself later on, so I was wondering if there's an easier way than creating a new page for each one.
thanks anyway !