All images used to create content (such as retouching, upscaling, and other content that involves not creating from scratch but restoring third-party images) on this site are either stock images and freely licensed, or created in Google AI Studio, which permits modification and distribution of the generated images, including but not limited to commercial use.
Main sources:
https://pixabay.com/
https://isorepublic.com/
Minor sources:
https://www.magnific.com/app