Pictureless Profiles

Hi guys - does anyone know of a plugin that can temporarily hide 'pictureless' profiles i.e. new profiles where the user has not yet uploaded their own avatar and keep the profile 'hidden' until such a time as they do?  My social site is working really well except roughly 60% of users are not uploading profile avatars - hence the site isn't very visually appealing.  Possibly the incentive that their profile won't be accessible to other site user (except Admins obviously!) might prompt such people to upload a picture - any suggestions?  Possibly a time limit whereby if they do not upload their own picture within 30 days of registering their profile will get banned might be a good option too.