Taken from Pbase Help for "Profile Page"
http://www.pbase.com/help/faq&id=176"Random Pictures
For paid users, four random public photos belonging to the user are displayed."
4 images are randomly selectly from among your galleries. Each time your 'profile' page is loaded by anyone, a new 4 image selection is displayed. 'Pat' is the name you have choosen to use for your Pbase account.
hope this helps