Market Press upload fields for Products

Hey Guys... I looked for a related post but couldn't find one. I see lots of people asking for the additional of image uploads using custom fields for marketpress. However, this is for the admin side of things.

I have a client that needs to allow customers to upload images when purchasing a product / service. Example:

Client sells greeting cards where the customer uploads their kids artwork as a jpg and the client then styles the art and makes greeting cards out of it. Prints and sends to client. We need a way to allow a customer on site to choose a greeting card product, then upload several images for that card.

Any ideas? Knowing you guys...you probably have a way to do this already..I just haven't figured it out yet.

Thanks!

John