Basically what I do is credit things I received for free. ( and no I do not have a gallery on site but in several other places.) When I pay however, I gave the vendor my thanks in money, I tend to pack a lot... very many and then some things into my images mix at least 5 outfits add anywhere from 20 to 150 props render then draw the rest by hand, I would take me too long to credit all the things  I paid for anyways. If however a free product was used somewhere in the picture that will find itself in the credits no questions asked.