Before using images found through search engines such as Google, check for information on copyright and fair use on the image's web site (e.g., FAQs or Copyright Permission section of web site). Most images are copyrights, and cannot be freely distributed. The best way to search for images that you can use on Google Images is to click on Search Tools and then select one of the "Reuse" options.
Many Flickr users have chosen to offer their work under a Creative Commons license, and you can browse or search through content under each type of license
When searching for multimedia (audio clips, video clips, pictures) on the internet, you should always assume that any media you come across is copyrighted, unless stated otherwise next to the picture or clip or on the web site. Finding any media on the Internet does not automatically grant you rights to use it for any purpose other than viewing or listening to the media on the web.
Before downloading or using any media, check for any copyright and usage restrictions. Most web sites provide information and guidelines for the downloading or use of media contained on the site. If a picture or clip is labeled as being in the public domain, then it is available for public use. Many websites also allow use of media for non-commercial or educational purposes only. It is your responsibility to follow the guidelines for the use of media from individual web sites. Some of the sites ask that you provide credit to the web site in addition to a link back to the original location.
Images that are free including those that are in the public domain or available via Creative Commons licenses.