There seems to be some confusion over public domain and copyright ownership.
Even though a photo/image is posted on a website that is viewable by any visitor i.e. the public it does NOT mean it is in the public domain and therefore copyright free.
Images may only be placed into the public domain by their creators, or they may be public domain because they are ineligible for copyright or because their copyright expired and this depends of the jurisdiction of the country where the images are used as copyright laws are different for example in the US from those in Europe etc. Placing an image or other content in the public domain is usually done via a statement on a website under Creative Commons license or similar.
So in a nutshell if the creator of the images ask for his/her images to be removed as they are used in breach of his/her copyright they are entitled to have them removed, however enforcing any breach of copyright is an expensive legal process and would have to be taken against the "publisher" in this case the forum owners rather than the poster. An unlikely eventuality.
Who owns the copyright to images place on an auction site would be determined by the terms and conditions imposed by the auction site as a condition of using the auction service. The creator might have agreed to pass copyright over to the auction site under their terms and conditions...who ever reads them anyway.
Bookmarks