This is a fantastic start as a new painter. Recommendations;
Pull out more details through additional detail work - Those eyes pop for example, look at the piece, what else can pop? Perhaps rolling with the red eyes you'd compliment it. For example, he's wearing a hood. Keep the hood and cowl brown, then make his under jacket a deep maroon. This will bring the eye to the details.
Keep rocking that rust/corrosion look. He's nurgle, plague bound. Maybe there's a green/teal patina you could add as well to give it a "snotty" feel on the metal pieces.
Keep working this! You've got more than the basics down pat.