The picture says it all, I guess.
Resolution: 5", 720x1280 px
Seems to work fine with an avatar.
Been trying to set up an avatar from my mobile with no luck, I just get this error: "Token verification failed. Please go back and try again."
I just changed my avatar here using my mobile phone
I tried again now and still the same error.
Just to make it easier to reproduce: did you try one type of avatar in particular? (gallery, upload, gravatar, etc.)
I tried them all but Gravatar