Digital and non-digital works are equally protected by copyright. Follow the rule that images on the internet are protected by copyright laws unless there is information associated with the content that states otherwise. Always consider copyright laws before using content from the internet.
Google is a search engine that helps you locate content such as images and photos. It is not a content depository, and it is not a collection of public domain or copyright-free works. Google points you to images and photos according to your search criteria. Once you find that perfect image or photo, you must take certain steps before you may legally use it.
See links below to websites that provide images and photographs available in public domain.