None of the relevant literature makes mention of this or any warrior on a snail. Though the characteristic coral necklace worn by the rider marks him as a member of the royal court, the meaning of the snail can, at this point in time, only be guessed. Considering the fact that animals tend to be closely connected with specific myths, however, the snail may refer to a story concerning the founding of the kingdom of Benin, recorded by the chronicler of Benin Egharevba (1893-1980). According to that myth, the god Osanobua sent his sons to live on earth and instructed each of them to bring something useful with him on his journey. While the older ones chose things like magic or riches, the youngest, acting on the advice of a bird, brought a snail shell. Upon their arrival on earth, the sons discovered that their useful items from the sky could not be used down below. The youngest son, however, was told by the bird to turn over his snail shell, upon which an endless stream of sand began to pour out; the sand flowed continually, forming an enormous piece of land over which the son then reigned, thereby becoming the ruler of the world. This object may very well depict that proud, youngest son of Osanobua - who would later become the founder of the kingdom of Benin - sitting on his useful snail or taking it on a victory ride to celebrate his rule.
"Many, many years ago, Odua (Oduduwa) of Uhe (Ile-Ife) the father and progenitor of the Yoruba Kings sent his eldest son Obagodo - who took the title of Ogiso - with a large retinue all the way from Uhe to found a kingdom in this part of the world. At the moment of his departure his father gave him a charm in the form of a snail shell containing some earth to invest him with absolute power and right eversince to the present day of every reigning Oba of Benin as the lord and owner of the land" (Egharevba 1936: 7)
Dr. Stefan Eisenhofer. Höfische Elfenbeinschnitzerei im Reich Benin, S. 28.