///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...
The term plagiarism implies not only that you published someone else's message, but also passed it off as your own. Thus, you have appropriated the author's right to the text, passing it off as your own. Thus, if you publish someone else's image, passing it off as your own, then it will definitely be plagiarism.