The legal risk is minimal; all of the big players in tech run such services after all, and there are tens of thousands of hosting companies that handle photos as well. You should spend an hour or two with an informed lawyer to understand what you need to do to protect yourself through the CDA and DMCA (including registering your agent with the copyright office). If you stay within the confines of what those laws provide, you're not liable for what your users upload. The talk with the lawyer is really advised if you want to feel safe about starting such a venture. "Policing" what's uploaded can actually create liability rather than relieve you of it, for example.

Thanks for the advice. What type of lawyer do you recommend for this? Any references available?

If you're planning on making this a business, the real risk is losing money, time, and failing.

That is a very contained risk I am willing to take for what amounts to a hobby side project. I am just trying to see what I would need to do to cover my bases and ensure I don't enter into a zone of unbounded legal risk (or at least prevent it to the best of my ability).

I don't know much about liabilities, what what will you do if you see child pornography being uploaded to your server (which will undoubtedly happen)? How will you filter / handle that?

That is certainly one aspect I am interested in HNs opinion on. Of course we won't be able to magically solve that issue, but I wanted to see what the current state of affairs is. As someone alludes to above, there are implications on even trying to police it vs respond to abuse comments. Just trying to see what the best step forward is.