rflickr is a Ruby implementation of the Flickr API. It includes a faithful reproduction of the published API as well as method encapsulation to provide more useful object mappings. rflickr features result caching to improve performance.
If you are building an image sharing service or a social network mashup, it's likely that you will want to incorporate face-tagging in your images. Maybe you'd like to go a step further and automatically detect faces in an image, similar to Apple's iPhoto. A Romanian developer has developed an API to help detect faces in images and return the box coordinates so that you can build any kind of app you want.
Streamzoo, an alternative to Instagram, has just released the Streamzoo API. According to the documentation, the API uses HTTP calls and returns JSON. It joins 341 photo APIs in the ProgrammableWeb directory.
Roughly a year and a half after Unsplash began opening its API to third parties, the company has opened the floodgates to its API. The company boldly opened up the API that the photo community Web app currently runs on. Further, API access is totally unrestricted and completely free.