Damn, too bad FloaterTWO didn't use hi-res tex I made. Low-res throws itself into eyes. Nice composition, tho if I were you I would not overdo contrast so much and use more lamps instead for a more dramatic darker look.
Don't have it saved sry, but I can write some tips. For lighting use a lamp with a regular round sprite selected, outside of frame. Point it at your scene and move it around (use camera tool to preserve the shot and move around). Lamps create more solid shadows and also add more ambient and dynamic lighting to the shot. In my "Come back" shot I have two lamps. One over top (dark-cyan) and one behind the guy (purple). The closer you bring a lamp to your object the brighter light becomes. Also the higher your cross at the colour pad to the top, the brighter your lamp will be.
I know about basic lamp tips, but I always mess up on the colors and FX, as I'm never sure what color filter to use (I have a pack from a video tutorial on Facepawnch and a few of my own) in my screenshots, or what color lamps to specifically use for specific shots/moods.
Choose colours according to environment. Night has lots of cold colours, so warm ones will make bright contrast. Day has more warm colours, therefore use colder ones and so on. It has a lot to do with intuition, there are no "proper" or "wrong" colours.