While copyright laws vary depending by country, the United States Constitution provides copyright protection for all original works, including but not limited to photographs, music, motion pictures, art, sculptures and computer software. All images created after January 1, 1978, in the United States automatically receive copyright protection with many images before that time also being protected.
Generally speaking, all original pictures should be considered property of their rightful owners and should not be used without the permission of the owner. This is not limited to whether or not the user profits by using an image. Taking the picture out of its original form, such as using it in a collage or compilation, generally results in breaking copyright law. Saving an original image and using it on your website without the owner's permission is illegal.