Amazon Rekognition - Add Amazon's advanced image analysis to your applications.
API List - A collective list of APIs. Build something.
The Unsplash API - No-limits, do-what-you-want API for access to 200K+ HD pics.
YOLO - Real-time object detection
Clearbit Company Logo API - Get any site's company logo with just a URL
CloudSight - Image recognition API; send an HTTP request with an image, get a description of contents.