Talking of scribbling, and with the Crimes of passion show in mind ... Today's Independent on Sunday "New Review" supplement has an interview with calligraphic graffiti artist Mohammed Ali.
Alas, the IoS print it in smallish white type over heavily textured orange and yellow wall, which makes it extremely difficult to read. And I've searched in vain for it on the Independent's web site.
I find Ali's (and others') use of Arabic letter forms as graffiti material extraordinarily beautiful ... as are the small Arabic and Urdu tags to be seen in many cities.
If you're near a copy of the IoS, and have a supply of Migraleve to hand read it (page 49 – Living). If not, take a look at some of the work at AerosolArabic.