Some sites, such as Overgrow (now defunct), claim "ownership" of all content uploaded - such terms are NOT legally enforceable.

Legally transferring copyright in most instances is much more involved requiring written agreements, including backup clauses that take into account that copyright ownership itself may not be legally transferred in some instances.

Bottom line is that the submitter retains "ownership" of the content they submit, including images...

However, by posting their content they grant us (similar applies to any message board they post on) the free, non-revocable* right to utilize their content in a limited manner; display on the message boards and related resources.

* one effect of the non-revocable part (implied even if not specifically stated) is that a poster may be precluded from later requesting their content to be deleted; we can and often will refuse such requests; most all content, including deleted, is archived, and such archives may be made publicly available at any time.

To be clear, the copyright for both text and images is still OWNED by the poster regardless of how much they share it with others.

Ron