I'm running a photography forum: members submit pictures to our curators who decide if their picture will be published or not (same as post moderation, but for pictures). This is why I need to restrict the number of picture they can submit during a period of time.
I would pay to set the number of pictures a person could upload.
This to me would be a GREAT add on for a subscription. Basic membership you can upload 1 pic. then members could upgrade for access to private areas, increase how many pics they are allowed to put in their profiles and so on.