AFAIK their artwork is pulled from all over - they do not keep track of individual scans/scanners. Nor which site an individual file was pulled from.
I appreciate why you feel as you do, Mr. Do. However, I constantly trawl for source materials, looking at lots of sites - only a small number track individual scans/scanners. The majority don't.
Tonight I grabbed a torrent of flyers, and looking at them it's basically a complete dump of Arcade Flyer Archive. This stuff just churns out there until someone uses it.