I think what I love best are the details--the Death Eater mask and the Centaurs' arrows along the ground beside each of them, symbols of the tribes these two characters have forsaken. I love the "filthy little mudblood" lettering, and the details to the zodiac. And the tenderness expressed between the two characters. Such a lovely touch to show Firenze taking care of a smaller Severus!
And the splash of color of the mandala around them. Such a nice visual focus.