Four hours with a mouse is fairly insane there, Jof. I'd be lucky to have this done in a month doing that... XD Lighting is loverly, specially around Samus. There's only one thing I don't really like about it, and that's the way everything is a little regimental. The Metroids are over there, Samus is there and the Gamma is there... they don't really mesh together into a single image, just three smaller ones beside each other.
I wanted to portray the characters rather small to sort of get across the atmosphere of Metroid 2, that is being along in an alien planet fighting Metroids. It's a massive place and it's easy to get lost in.
I have to say the detail and lighting are very stunning. (Let alone the fact that you did this with a mouse o_O ) I just find it intriguing that you put more detail into the characters rather than the background.