Any photographs that you did not take yourself will require copyright permission, and you should not include photographs of human research participants. We also recommend blurring the faces of people who appear in your photographs, unless they have given you permission to take their picture for your thesis.
Images and photographs found through Google Images or on websites such as flickr.com are never ok to use without permission. You will need to determine who owns the copyright to the images you wish to use, and if they haven’t indicated that it’s ok to use them for commercial use, you will need copyright permission to publish them in your thesis. Sites such as Flicker.com or Wikimedia Commons allow you to search specifically for images that have been released for commercial reuse.
The UBC copyright website maintains a list of websites and resources where you can search for images that are public domain or released under creative commons licenses. Use the "Public Domain and Creative Commons Resources" tab to explore these resources.