Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein.
They are also known as "royalty-free digital stock photography communities."
These companies don't pay as well as traditional royalty-free photo companies; however, they also don't employ the same strict restrictions as full-fledged royalty-free agencies.
Royalty-free images are given by photographers and artists to the public domain to be used in whatever way you like.
Search for neat, royalty-free images on the Internet and then copy and paste them into the graphics application.