You don't need Saas for that. Just upload the images in a S3 bucket and set the access to protected. You can make a PUT request to a pre-signed URL for that. For GET just create a lambda function that GETs the image if it passes your criteria (create time, secret key). It's less than 5 lines of code.
As for CDN just put everything behind Cloudfront and you have edge servers worldwide!
As for CDN just put everything behind Cloudfront and you have edge servers worldwide!