Documentation:Intellectual Property Office/Image Sites
Images are "created" by photography, graphic artists, cartoonists, computer generated images and other media. Each is protected by copyright for one or more sources. For example, a photographer who takes a picture of a sculpture is the creator of the photograph while the sculptor is the creator of the subject. Where a photographer takes a picture of another person or a trademarkable building or other image there is copyright in the source as well and a model release is required.
There are many sites which host Royalty-free images for use in projects. This does not mean that the images are free to use. There is a one time transaction fee payable for use of the image in a project.
There are some sites where the images have been released through a Creative Commons License,permission is provided for educational use or similarly have been put in the public domain.