Fantastic, I love everything about this from the head, armor, even the weapon choice - awesome work. I would love something similar like this as a tattoo but nobody I've seen captures what I want like you have here.
I still can't get over it! Here's a crazy idea: go pro if you are not one already. (you know, movies, book and magazine covers etc etc etc)
And here's an insane idea: could you make a centaur with 4 (four) arms? I've always wondered: 4 legs, why not 4 arms? Great speed and stamina for running, why not great manual strength and ability also?
Oh, and I've always imagined: male centaurs: body of a bull /buffalo etc; female centaurs: body of a horse /filly /mare. So this centaur's tail is just fine by me, "just like I imagined - NIN"
If this is just a hobby of yours, I highly suggest you go into Concept Art for Game developers. They would flip if they saw you're gallery...the entire thing is just so overwhelmingly creative. Getting back on track, I'm in love with the centaurs hybridized look here, like it's not just a straight human torso--it has animalistic features which you've integrated perfectly into it's design. Great job! :3