Heres some sites for you
http://users.ox.ac.uk/~peter/humour/graffiti.html
http://www.gelfer.net/graffitisample...%20graffiti%22
And if you want to have a go at a bit of graffiti without having to worry about bumping into
Robbie Williams try this site:-
http://www.blograffiti.com/all.php
These are for you Granny, (whatever you do don't go looking for animated toilet gifs, there are some very strange sites out there)