Thank you for a very nice instagram viewer, sharing works perfect also!
If you want to try something with actual uploads there is a rival to Instagram called EyeEm with clients for ios, android & windows phone. Browsed the API and it seems to support uploads and filters:
https://github.com/eyeem/Public-API#eyeem-api
You need to register an app:
http://www.eyeem.com/developers
Just an humble suggestion since you did such a great job on instago.