Oh boy, where do I start. First and foremost. Nice job on the characters, and more importantly, there expressions. Without this element, this drawing wouldnt be what it is. Though to me twilight looks a little awkward, but thats just me.
Second, tbe shading is very nice. Im always a fan oc good shading technique, manily because im trying to find one myself
But the thing that I like the most is the textures: it gives this drawing the feel it gives off. A warm, steamy feeling that would otherwise be absent. The rock wall in the back actually looks like rock. Why im so fascinated by it, I don't know. But thats good.