You may not be familiar with this story, but I am strongly reminded of a scene from Steven Erickson's Malazon Book of the Fallen.
The wizard Quick Ben Travels to the bottom of the Abyss (an alternate plane/dimension) to meet Hairlock, a wizard who died an transferred his soul to a puppet. His time spent in that place shattered his sanity, from memory.
I guess if was the concept of depth that triggered the memory. I see the orange blobs in the foreground as fish swimming through a see, and the spiral in the centre reminded me of one of my sketches: fav.me/d80l9qo.
In any case, the painting has interesting elements that made it a powerful experience for me.
Luna really the best pony to use as Jack Skellington and I've seen at least four other casting choices.
I've seen Twilight, who'd work if Luna weren't just so well suited for the role I've seen Pinkie I've seen Rarity (that one had Spike as Sally, Twilight's had him as Jack's dog.) I've even seen Rainbow Dash
Luna however works best as The Pumpkin King of Halloween Town or we could say, the Lunar Queen of Nightmare Night.
That's pretty impressive. While I rather prefer less chunks of paint and a more gradient look, this is really interesting. Keep up the good work! Also. If you feel like it, try a oil-on-acrylic painting. By that, I mean make a background in acrylic paint and then add the foreground/characters/objects with oil paint. It's really fun to do.