I am using Node.js on Heroku, and use MongoHQ for data.
My app needs to be able to store image files, that are uploaded from the user or pulled down from other sites. I'm not looking for add-on to do image processing or the like, I just need to be able to store them and serve them. It is fine if I just reference them from within my Node app as a numerical id or the like.
Being as this is a one-person, self-funded project, I'd like to do this as cheaply as possible (I don't want to pay a lot of fees for add-ons) and prefer keep everything on Heroku for simplicity (although the latter is not a requirement, just a preference). I know I could store them in Mongo as binary, but I'm looking for something more efficient and hopefully cheaper per meg of storage.