Cloudinary - Cloudinary is a cloud-based service for hosting videos and images designed specifically with the needs of web and mobile developers in mind.
Cloudimage - Cloudimage.io is the easiest way to resize, store, and deliver your images to your customers through a rocket fast CDN.
Sirv - Dynamic image processing, hosting and rich-media for retailers and eCommerce.
Gumlet - Optimised Image Delivery Made Simple
Uploadcare - CDN, content delivery, content delivery network, file handling, image processing, cloud storage.
Piio - Generates responsive images so you don't have to optimize