Basically I do not see an issue here. Your server must send php mail and 2 things need to happen here. In admin options in admin you need to have this set to YES
Allow users to be notified of new posts via email?
Then a user needs to explicitly mark yes to be notified of all new comments on there photo when they upload it. This will insert a notify insert into the notify table as seen by this code in image-inc.php when a photo is uploaded.
Content visible to verified customers only.
So again the global switch to allow notifications needs to be turned ON and the user has to specify they want to be notiffied and your server needs to send out email. I have tested this every which way and it works fine.