I'd love to learn how you are handling media/photo storage from both a technical and practical perspective. Some questions that come to mind: are you using a dedicated service or did you build it yourself? Are you using a CDN? How do you plan to deal with abusive content and the liability that comes with storing photos?

I am also working on an app where hosting photos would be a nice feature - but the risk/undertaking without proper and potentially expensive infrastructure is daunting.