The pages are not actually pages, but what DNN does is use a property editor that automatically creates what appears as the user profile when you go to manage profile.  To add support out of the box for images would require you create a new handler for that data type ... something that's quite complex.

I would advise you never to customize core.  You want to always be able to update to the latest DNN for security and functionality reasons.

What would be best is if you just created a custom Manage Profile module and extended it to your liking.