Images are spread over the web for a reason that of which is to provide people various abstracts and expressions for personal or commercial use. But while there are no obligations and copyright violations for people who make them available over the web, providing due courtesy through link backs is the best gesture that people could at least do.
Acknowledging the efforts, creativity and generous ordeal that people who want to spread over the web through link backs does not take much effort. Giving due credit to where it is due for these people is something that is already rewarding in a sense instead of utilizing files and stuff for personal gain and glory.
Some sites would require that pictures, images and music files to be uploaded and not linked. However, even after downloading them, link backs or even a simple note pointing towards giving credit to the original author and owner will surely be appreciated by the latter, practicing the ethical way of using files that are available on the web as placed by such people.
[tags]links, trackbacks, linkbacks, images, mp3, music, photos, plagiarism[/tags]