customisation of store product upload

I require an amendement to the store during the product upload process... you get the option to add file, screencast, photo etc... I need a number of extra fields adding... 4 in total.

I then need the fields to output on a jpeg background that becomes available only on the successful purchase of the product.

The idea is I have betting tips site and I want the extra fields to output onto a betting slip in a script font to look as thought someone has written it out as a slip.