What sold me on the reference photo for this painting was the feeling like Emily-Rose was emerging from the darkness.
Lost edges. I love the idea of lost edges. So, if you look at the top left of this painting, you will see that there is no defined edge to her head there. You can't tell where your head ends and the background begins.
I love to include lost edges in my paintings if I can, because they add a sense of mystery. It feels to me that my eye gravitates there and then my brain wonders what is in that black area. It will make more sense when it's done.
(I hope!)
On another note, I prefer to make my blackish colours rather than use black. I find that blacks often have a harsh look. I also don't like how they copy. I am fairly happy with the blackish background on the right. I started with a layer of a dark purple and then scribbled in layers of very dark green, red, blue and brown. I may still add more green and brown to warm it up a bit. We'll see.