I like the orchestration, you definitely achieved the Nightmare Before Christmas vibe.
I think you've already reached the point where you mixing is never bad, I can't recall any mixes of yours that seemed to be missing something. You're like me though, you want some more polish on your mixes. If you need some more research material, you could check out The Mixing Engineer's Handbook by Bobby Owsinski. I haven't finished it yet, but I've learned quite a bit already. It covers pretty much everything.