Basically if you right click an image on windows there is always something as view metadata, sometimes it has date, software used, nanevof original file and more, so you can trace things on them but if you export your pics there are app to include info like your site. If others reupload it those metadata unless removed are there. I have a personal script so my system does not work in other computers as it was done by hec but it is easy, look for how to see metadata or add. Most thieves do not bother in checking them