I don't usually credit images as the majority of the time, no joke, I don't always remember everything I used in a particular image or image set, not to mention that I prefer to post fairly quickly (not only on this but other sites as well).. I would spend an additional 20 minutes to track everything I sometimes use in a piece then type it all out, then make sure I hadn't forgotten anything.. then laughing lose it all when I click preview or submit, and left out some checkbox   =)

As a vendor now myself, I don't mind if anyone does or doesn't credit.. I thank folks for the purchase in my readme files and I thank (in general terms) the vendors who made the items I use in my promos.  If someone made the purchase, I hope they like the product enough to use it.