Once a copyright free image is published to the web it becomes part of the public domain. This means that a user can utilize the image as they see fit. Attribution or payment to the original content creator is not necessary. After publishing an uncopyrighted material to the web anyone can copyright it. Now web sites state at a picture that "the image may be copyright material ". Public Domain opens your material for anyone to use freely if it wasn't copyrighted before posting it. There are "Domain Free" publications and sites for anyone to use without danger of being sued. If you want to retain ownership of your items, I recommend that you copyright them so you'll have a legal document of proof from the Library of Congress otherwise a magazine, card, calendar company, souvenir company making cups, plaques, etc. as well as fabric companies and any number of companies that use images can syndicate them using them on whatever they choose. If that happens, you'll lose royalties that you might otherwise have been entitled to.
China has been stealing designer crafts and photos for years. When I had my website, I would check the viewer stats report quite often. Chinese lookers would show up from time to time searching for a particular item.
I have around 50 copyrighted how-to craft and decorative painting designs and instructions. If I sold one to a particular magazine, that magazine owned the rights to the design and instructions if stated in the contract. In otherwords, they are purchasing the rights of ownership. Therefore, I lost the ownership rights to that design and could no longer use it for anything. There were a few magazines that would purchase an unpublished design but would not retain the rights which I could not use or publish until six months after publication at which time the rights reverted back to me according to the contract.
I don't know the content of your images or how well you want to retain ownership but t's your decision as to how important they are to you.
