That's a good start, but firefox will let you walk every image on a page just by banging the forward button, and if they land on pussy1.jpg from somewhere else they can still walk all the sequential files with a firefox toolbar called "browse images". You can't really do anything about the first, but you can thwart the browse image toolbar by naming files like this -> 01-pussy-20.jpg 02-pussy-19.jpg 03-pussy-18.jpg etc.
It takes about 5 minutes to do a directory with an app called "lucas rename". There are lots of batch renamers out there, but lucas is the only one I've found that isnt too stupid to know that 1.jpg goes before 10.jpg.