Credits in the skins would be just fine HoZy (Thats why there is a credits field)
And no it isn't only a skin. Some of the artwork used has taken someone alot of time and effort and is a form of art, be more respectful to the creators/owners of such art, unless of course you have spent weeks rendering a scene to perfection and given it away for free, in which case I will shut up.
All I ask is that people give credit where it is due on the artwork. As a renderer myself, I know I wouldn't be happy seeing my work posted here with no credits.