Hi folks, and nice one, MG!
I've no time at all for this, but I can't resist something so close to my heart (having a partial origin as a famous graffito myself )

1) First seen outside Sussex University back in '81 (ish), now all over the Web:

to do is to be
- Descartes
to be is to do
- Sartre
do-be-do-be-do
- Sinatra

2) From a urinal somewhere:

Preserve nature - pickle a squirrel

3) And on an entirely different note, from a billboard near Camden Lock, London (c.1987)

* ENJOY LIFE *
This is not a rehearsal

Probably loads more... I'll try to return bringing 'em

Fisk