I both buy and sell here at Renderosity. My dad makes most of my purchases using his credit card and an account he made to buy me things. I worry that this same thing could happen to me. Since the item would be purchased under his username and displayed in my work. I really don't want to be attacked by people saying I have stolen their product. Now for the vendor side of me, I would never make a stipulation saying that an artist had to give me credit for using one of my items in their work that they paid good money for. As many here have said once the product is bought it can be used any way the artist wants. I would just be happy to see it being used.