It's so easy to find images on the internet, but that doesn't mean that you can freely use them without the permission of the creator / owner of the image, be it a photographer, an artist, a museum or other group, organization, or institution. Use the resources we provide below to find images you can freely use in your project.
We recommend that you start your image search with the subscription database Britannica ImageQuest, which contains millions of images rights-cleared for non-commercial, educational use.
On your image search results page:
Best Practices for Attribution with examples; from Creative Commons.