No. Not every work without mention of the author is considered as an orphan work in the sense of the law. First of all, it must be a phonogram or audio-visual fixation. Secondly, this work must be included in an archive made accessible to the public by an institutional or broadcasting organization. Before reaching the conclusion that the author is not known or reachable, the user must have carried out some research and give prove of diligence in doing that. Moreover, before using it without the consent of the author, the user has to notify the existence of the orphan work to the collecting societies and in principle pay a compensation. In this case, a single picture found by a private person on the Internet, which is not part of a public institutional or broadcasting archive, is not considered as an orphan work, and cannot be freely used.