Another thing worth mentioning is that this site is already saturated with "advertising" ;o).

Edit: It's not complicated. Not at all. When I do a render I try my best to mention what I used in it, but to require it is another matter entirely. Those people paid for their products and as such can use them however they wish (according to the license). There's no expressed implication in the license that one must credit the vendor they purchased from in every render they created with said item. For what it's worth, I've also seen something in a render that I like enough to buy and don't know who did it or what it is. At which point, I contact the person who did the render and ask them ;o).

Laurie