Texas  |  Intellectual Property

Usually yes. However, just because it is on the internet unmarked does not mean it is unprotected. The photo or schematic could be copyrighted (copyrights are automatic) and the copyright could even registered and in force and valid and yet not have a notice. Copyright notice and registration are optional, although the copyright is difficult to enforce until registered. You would normally not have any liability until you are actually know or are notified of the existence of the copyright. Recognize that when you copy such a third party item, you could have to change later if you are notified of it being copyrighted. If the photograph is of a person, there may be privacy rights or celebrity rights to consider.