I've managed to add an extra field in the Purchased Files page, as well as hide the address limit, however I cannot figure out how to actually get the product thumbnail in there, like there is on the cart page. Below is what I'm working with so far, any ideas how to get the image associated with that file in the empty field?
You need to change page callback for path
hook_menu_alter() and your custom callback should be based on code of
uc_file_user_downloads() function, you need to change it, add new column with product image. I guess you need to change query in that function to get more data from 'uc_file_products' table about the product id, and based on that you can get all product info etc