There is an entry on Yarilo in The Joy of Knowledge Encyclopedia, Vol. 53 (Fact File: XI) and it reads:
"Yarilo, in Slavic mythology, a god of spring and regeneration and of sexual love. He was depicted as a flower-crowned young man on a white horse. Each spring a planting rite was performed in his honour and in summer a ritual was held in which his effigy was ceremonially buried."
On the contrary, the description above differs largely from this half-naked, sword-bearing Yarilo. The flower crown on his head is correct but I believe he has many representations, though.