Pictures which are not subject to copyright protection are those in the public domain. Public domain images include works that have been released by their owners for use of the general public. A desired picture may not readily reveal if it is public domain or not which may necessitate further checking of copyright status, if any.
Copyright law allows for the “fair use†of any pictures without the need to seek permission from the owner. This would usually include non-profit seeking purposes such as for a school report or for a community activity. Thumbnail images lifted from other sites have been declared by courts as falling under “fair useâ€. There are of course other considerations like the number of times it was used and how it was used.
Since copyrights to an image is not always clear, determining whether it is public domain or not may be tricky. Generally, photos that are considered public domain includes government photos, photos taken after the year 1989 except when otherwise stated, photos with expired copyrights, and photos posted on public domain websites. These sites are quite clear about the restriction-free nature of their posted images.Â
Once an image is declared public domain, it can be used for any private or commercial endeavor subject to certain restrictions of owners when applicable.  Sites who offer these images typically requests for link backs or any credit, although most are not compulsory. Images with higher resolution are also usually offered for a fee. Public domain images collected in a site may come from various sources. Public domain pictures should stay as such and persons who have used it cannot claim copyrights on them.