Imgur - Imgur is a free and simple image hosting service with image editing feature. Signup is optional.
Uppy - The next open source file uploader for web browsers
Flickr - image and video hosting website
Filestack - Simple file uploader and robust APIs for uploading, transforming, and delivering any file into your app. Filestack is a collection of tools and powerful APIs that make it simple to upload, transform, and deliver content.
imgbox - Imgbox is a free image hosting service.
Uploadcare - File uploading, media processing & content delivery for modern web apps