I don't know if someone wants to use a picture on the internet without providing a link to that picture, if that user will be banned for his action or I must also provide the link to that picture which I used. Is using someone else picture without providing the link also plagiarism.
If posting a Google image or a ransom image from the internet without citing the original work was a problem or appeared to be plagiarism on the forum, everyone would have been banned by now because most of us have uploaded an image without stating the source, it only becomes a problem on the forum when someone steals an art to participate in an art contest and claims it as original work. Image plagiarism is mostly enforced in academic works, forums and social media do not follow this norm.