Just a little attempt at making a nighttime scene. The stars are made by a UV sphere cut in half, with the vertices randomly placed, with a halo material. Sky is a dark blue to black gradient. The lamp has a light blue color. I also have AO Ray trace with plain color.
nice, looks like a Disney night 
Good job, a bit too blue perhaps, but good nontheless.
for me, a negative hemi combined with a spot worked pretty well.
Daniel
Not a good job. It is just a monkey under a black light. A night time scene is more complexer than that.
You should really download one of those lighting challenge scenes from Jeremy Birn to build a night scene. A simple plane and a monkey on it could mean anything.
A night scene is not about blue light. Those are the 1980’s gels in front of a lamp to color the scene blue. It looks damn cheesy.
I would construct a night scene as follows:
Night scenes are high in contrast (some moonlight, although moonlight is strong enough to illuminate the area and cast very strong shadows), some light from outdoor lighting. These light has a short fall off distance. Decrease the hue in the distance in the compositor. Most things in the background would be only visible as dark silhouettes with a shimmer here and there, but the foreground, where the object of interest is should be relatively well illuminated.
Most of these effect is about mimicking a real world camera, so a real camera would have a longer exposure resulting in a more pronounced motion blur and shallow depth of field.
Hope this helped a little.