"The thing is that in photography and painting you are hardly ever using the result of someone elses artistic vision."

But that texture also requires someone elses artistic vision as did the mesh that the texture was created for, etc, etc. It's a never ending subject. :-)

I think crediting is a good idea especially in galleries. I personally try only to download and purchase items that allow commercial renders simply because I don't want to keep track of separate folders or have to track down someone who's moved web addresses etc. If a readme file states "personal use only" I don't extract it.
Daz's free models for example, while I don't feel it necessary to "credit" what I buy, they have the same terms for their free models as they do their purchases. They offer the free models knowing they will gain customers that way and it works for me. :-) If nothing else people may want to know where they can find certain items. I know if I paint a texture I like to mention it.

But if I were to put together an image for use on a t-shirt, for example, using only items that allow for that or my own textures etc, I don't feel the need for a list of credits. :-)
If you can, you should. If nothing else credit the main focus items.

...... Kendra