Very interesting project! Ukrainian graffiti artist Teck did some walls in 2012, in diferent places, picturing the 4 evangelists.
For those who don`t know about the importance of the evangelists and their symbols, feel free to check the folowing wikipedia-article: The Evangelists.
Here a list, which symbol belongs to the evangelists.
Matthew - Angel/Winged man
Luke - Ox
Mark - Lion
John - Eagle