Not to be a total stick in the mud but I have a few crits.
Take these for whatever they're worth since I might be the only dork to notice these things.
First of all I really like the mood/concept/overall a lot.
But a few drawing quibbles that aren't working for me:
- Horse's head is too big for the body
- From chest to ass isn't long enough
- The dude is too big proportionately to the horse
I might try a more animated pose for the rider since your style feels pretty fluid I think the composition could benefit.
Not that I think everything must be drawn academically correct, but the things I noted didn't seem to be a stylistic choice, just something that happened.
But again, overall I dig. I wouldn't levy the crits without the love :)