I really like the depth and composition of this piece! Some things are hard to tell because of the colors though/. The ears of the slug don't stand out too much from another, and the sky and castle both having pastel orange as their color makes it hard to tell them apart too. My suggestion would be to cover the entire thing with a black layer, lower the opacity (set the blending mode to "color" if you use csp) and see how you can fix up the values! Hope I explained everything well and good luck!
oops I made a small mistake I wanted to write "the ears of the slug and the sky don't stand out too much from one another" originally. Sorry I type fast and English isn't my first language ^^;