Libations for the Dead

The lekythos played an important part in Athenian funeral rites. Most lekyythoi (the plural in Greek) served as offerings to the dead. They were placed in graves, or on the steps of the grave stelae, and used to anoint funerary monuments... images were often applied on a white background, perhaps designed to evoke ivory, a material associated with funerals in ancient times...

Source:
http://morbidanatomy.blogspot.com/2013/08/libations-for-dead-lekythoi-at.html