Originally Posted by BoyAlley

NO. Since the original image itself that the thumb was created from does not trigger 2257/4472, the TGP owner has no obligation to obtain and keep docs on file since he has produced nothing originally based on sexually explicit imagery. HOWEVER: If the TGP owner takes an explicit thumb or image from the gallery and crops it so that it no longer appears explicit (aka cropping only the face out of a picture that depicts a woman getting fucked), the TGP owner has "produced" a work based on an image that does trigger 2257/4472, and as such does need to obtain and keep docs on file, even though the resulting thumb itself is not explicit.