Growing up back in the USA, I don’t recall ever seeing or hearing of Rebbe Nachman or the Nachman M’Uman graffiti. Breslov Hasidim were those guys who came around asking for donations and handed out booklets of Breslov teachings. In Israel, you can’t go far without running across at least one of the ubiquitous Nachman slogans.
There’s a great Wiki article that discusses in detail the origins of Bresolver Hasidism http://en.wikipedia.org/wiki/Nachman_of_Breslov
(Tens of) Thousands of Breslevers and Rebbe Nachman lovers travel yearly to Ukraine to Uman, the burial place of this Tzaddik. The Breselov Hasidim believe that there’s some magic in saying three times “Na, Nach, Nachma, Nachman M’Uman” as a verbal amulet for good luck. They also make sure to spread the landscape with painted graffiti, bumper stickers, and posters with this saying.
I remember one day I was driving in Tel Aviv and saw a hillarious bumper sticker “Na, Nach, Nachma, Nachman Bialik”, who was the secular poet and author of the early to mid 1900’s, and is considered one of the founding “literary” founders of the State of Israel.
Here’s one of the often-seen Nachman M’Uman signs in South Tel Aviv, not too far from the beach.