Thanks for curating this nice list of websites to look for free stock photos. Interesting how you mentioned about Unsplash API and its application to build AI apps.

We built an AI-enabled App using some of the popular Unsplash images which can tell you how likely your photos will become popular before sharing on Instagram or Facebook. Our AI essentially matches the features of your photos to the trending images on the internet (Unsplash’s API being one of the sources) and scores them on the number of matches. It will be great if you can check out this interesting application and let us know your feedback:

https://cornea.ai/