Guidelines for determining copyright.
Images--photographs, clip art, drawings, graphics--are usually copyright-protected. Determining the copyright owner for photographs is sometimes difficult. In general, the photographer is considered the owner even if the work was for hire (such as photographs of a wedding or other event). And the copyright endures even if the photographer is no longer living--rights can be transferred by a will as personal property. The photographer must specifically transfer the copyright, in writing and the document must be signed to another person.
Stock photography and clip art sold in books, on Cd's or down loadable from web sites is royalty-free(or may be in the public domain) but usually is not copyright-free. Exercise care when using the images. By reading the agreement or license that accompanies the image or is available on the website, you'll understand what your rights are for reproduction of the image and whether there are limitations on use. The most common limitation is for incorporating the image into something you intend to offer for sale.