Dionysus is the god of the grape harvest, winemaking and wine, of ritual madness, fertility, theatre and religious ecstasy in Greek mythology. Wine played an important role in Greek culture with the cult of Dionysus the main religious focus for unrestrained consumption. The earliest cult images of Dionysus show a mature male, bearded and robed. He holds a fennel staff, tipped with a pine-cone and known as a thyrsus. Later images show him as a beardless, sensuous, naked or half-naked androgynous youth: the literature describes him as womanly or "man-womanish". In its fully developed form, his central cult imagery shows his triumphant, disorderly arrival or return, as if from some place beyond the borders of the known and civilized. 

This sculpture is less about the actual man himself, because he is fairly similar to the other sculptures at the National Library of Russia, but more about the grapes and wine. It is quite a modern approach to make his hair out of this fruit, traditionally we wouldn't normally find a depiction like this.