Creative Commons licensed and public domain (copyright expired/free) images are excellent alternatives to copyrighted images because you do not need to pay nor obtain permission to use them (visit the page on Creative Commons & Public Domain Images).If you are unsure the copyright status of an image and/or if your use falls under fair dealing, you should request permission to use from the rights holder.Using an image for a decorative purpose does not fall under fair dealing.For example, when you need an image to illustrate a concept or provide an example for a topic, and your project is for an internal educational use. Depending on your purpose and context of use, you may be able to copy and use an image under fair dealing (more information on Fair Dealing).For instance, watermarked photos should not be used without authorization. Stock photos and photos by professional photographers require a licence or payment to use.

Note that a majority of images found through Google and on the Internet are copyright protected. Many people like to use Google to find images for their projects.

Google advanced reverse image search