Hi
I'm a python/django web application developer.
I took at look at your specs and all seems fairly straight forward. I can create the API system using django and django-rest-framework. Upload via AWS EB is something I have done alot, so there are no issues there.
User management, signup, password resets are all not a probelm, nor is the image pool. Where your pool of images is stored may be a bit more infrastucture specific. For AWS, there are modules to allow for uploaded images to be stored on S3 rather than locally.
Please contact me if your interested in me working on this.
Thanks
Marc Nealer