Pixeltuner: I love the colors you've chosen and the overall vibe of the piece. I do feel that the pose does not transmit evil. His arms make him look reluctant (all four of them). Stand in front of the mirror and think of a more aggressive king.
Hey Eofn, just to not get too deep into this design and avoid making a mistake...when you say crown do you specifically refer to an object inserted on the head of mr. satan or can we get creative as to what the crown is made of and how it wraps around his/her head?
The crown needs to be separate from the creature itself (ie, not just spikes or a part of the physical structure of the being), it's an accessory. It must be on the head but can be wrapped around the skull, sitting on to, floating, embedded - it's really up to you. As for what t's made out of, that is up to you as well.