An image custom field just appear after payment

Hello,

I need that an image custom field just appear to the final user after the payment are confirmed. Then, on the administrator page I can upload an image that the user can see on the order page. However, when I create a custom field to appear on the order page, it happens to appears before the user even make the payment, on "my custom fields" page. Although, I need that the others custom fields appears before the payment.