I was uploading a simple .jpg of about the same size and dimensions as those recommended and already in the repository. I tried a few different photo sizes and types with the same result, so I’m not sure what the underlying issue may be. Unless something has changed dramatically, my one guess would be to check the storage limits on the hosting account. I’ve seen that sort of failure before when running out of physical space on a host.
Incidentally, from a security standpoint, I’ll mention that it appears one has the ability within that interface to delete others’ previously uploaded photos. (May want to look at that as a potential future improvement.)
Hope you’re holding up!