Russia, 15th century icon: obligatory text over image
Icon in Orthodox Christianity is conceded to be not finished if Jesus, Virgin Mary or saints are not named.
Traditionally text over image is placed above or around the head stating the name of a saint.
Names are written in Greek or Church-Slavic language with very special style of writing and unique conventions about writing, making texts looking very different from mundane writings.
One of such conventions is the use of so called titlo (see more at wiki http://en.wikipedia.org/wiki/Titlo), which is used deliberately to write names of saints.
This Russian icon has been painted at the end of 15th century, and it clearly demonstrates described approach to naming.
Modern tags help to make the text more understandable.