It works both ways. Plenty of other sites via "links" link to this site.
It is different if the image is not simply listed on a public domain sale site. Photographs are subject to copyright.
I'm sure Blocker wouldn't be to impressed if all content from this site was STOLEN to display on another site to make it easier for people like you.

ebay, gumtree etc the people expect and most likely want the free exposure. On a private thread on a forum or website they don't expect or want you to steal their images, nor is it legal.