I'm on pc , and if you take pictures with PHOTO MODE wich is inside the game , then all the pic are hosted in photo Mode (check at the top ) . Once there you create an account (or tie an existing one) and voila ! you can view your pic there and download them and such .
if you do take them with something else , like say STEAM..then they be on steam .
oh and once you are in your account on Photo Mode (https://assassinscreed.ubisoft.com/g...-us/photo-mode)
you download and host them here . you can share them with Twitter and facebook , but thats about it . I dont use either..so I just download them and re-uplaod them on a free host like Imgur .