Very cool idea - starting a conversation on an image.
The issues I see:
1) The image(s) are easily obscured by comments.
2) Alerts, alerts everywhere.
I could see this having a very broad appeal to any type of community that uses images. Making an image and submitting it to reddit may be a great way to get traction (the image would be the marketting, the conversation would be extra).
I liked being able to comment anonymously and was disappointed when I couldn't continue to do so on the creepy house pic - I could see this really taking off.
Good Luck!
