Are you looking for free and open images? Here are some websites you can refer to.
Note: Before using these sites, always check the terms and conditions for the website plus the licensing information for each file before downloading and using. Remember that attribution is always required. If you are unsure if you can reuse a resource, contact the Information Officer (Copyright & Compliance) for advice.
USC staff have access to more information on MyUSC about finding images (login required).