Firstly if your integrating PP with VB
then you must configure your usergroups via PP admin > administration > Edit Usergroups
While there you'll see options to enable uploads per usergroup also disk space, file size and daily limits all very tweekable to suit your needs, in your case i would enable a filesize limit of say 100k maybe a daily limit, also concider your "Disk Space Limit" very important for you seeing as you have so many members already, if you went for say 1 meg per 'registered' member you could be ok, enable higher diskspace limits etc for different usergroups, offer incentives for using subscriptions via vbulletin also.
Once your Usergroups are configured correctly you'll see the 'upload photos' link in the menu.
Hope this has helped you.