I am fairly certain that the only way Sleipnir could work functionally as an 8-legged horse is if he's spidershaped. Otherwise, where in the world does Odin sit?

Anyway after a series of comically ridiculous sketch attempts trying to make an 8-legged horse actually look impressive, here's where I ended up.

 

I do tend to work too dark in digital, makes it difficult for prints to come out right. I'll have to tweak it a bit before I can run any prints, but I'm thinking postcard-size?