Very good composition and lighting! Personally I think the concept of "light" and "dark" is not connected to "good" and "evil". Light and dark are merely powers, and power can be used for good or evil depending on the individual.
Usually is is connected because of stereotypes and clichés; which, let's face it, those are boring and overused. Historically speaking, humans fear what we cannot understand, and we often kill what we fear. Ancient humans likely feared darkness (literally, night) because there were many unknown dangers that they didn't understand; thus they created stories of demons and evil creatures to explain what they couldn't (at the time) explain, and thus, evil creatures were connected to darkness. When evil creatures were connected to darkness, negatives (greed, lust, rage, etc.) were simultaneously connected to darkness.
In modern times, people have a better understanding of things we used to fear. And creative minds began assigning "darkness" as a supernatural or magical power that could be used for good or evil (though often evil due to its previous archetype) in fiction, i.e. Bleach.
Sorry for the rant, I had a random inspirational moment there
I like your way of thinking, and I completly agree with you Nowadays we're recreating a lot of these stereotypes e.g. vampire or werewolf standing on the good (human) side, fighting with the inner beast. People are searching for something new, because all old stereotypes seems to be childish. "An evil vampire lord murdering innocent people? Wow! What a fresh idea!"
But still if you're going to draw an evil creature you'll probably pick colours and symbols which are clear and easily readable for your audience i.e. connected with stereotypes. Without the story standing behind the picture it's really hard to present the evil/good character without using well-known symbols.
Yes, yes, you know--someone dressed in unimaginably cute, adorable pastel colours, while they assemble a bomb and...and...okay, so it is a bit far fetched, I admit. But it's just a thought it's probably better to stick to drawing evil characters as looking sinister.