When viewing a user's details within the User Group admin tool you will see a Photos column in the Current Auctions and/or Current Classifieds sections. Next to each live listing is an increase link within that Photos column. Each time you click this link the maximum photo count for that listing will increase by one.

This feature is really only useful if you charge you clients to attach some or any photos attached to their listing. Each listing has a maximum number of images that can be attached to them if there are charges to attach files to listings. And this allows the admin to manually increase this amount.