Ok, I feel bad. It's been like forever, and I haven't put any updates here since that inane Skeletor drivel. So...
Here's an update!
I've been learning a lot lately about color and lighting. This is one of my first successful attempts.
this tutorial. The most useful piece of information for me was about half-way down the page: the author talks about lighting and how to shade it. Gold-seven points out something I hadn't thought of before: all light has a color. And that fact makes sense of something I'd heard a lot before: "shade in a complimentary color." See, I didn't realize that the shadow's color should be opposite the light's. I had thought of it as a compliment to the object's color. So, on a red ball, the shadow would be green; on a blue ball in the same scene it would be orange.
You can see I tried a bit of that in this picture:
Notice that it looks fairly muddy. I mean, there are more problems here than just the lighting, but the shading isn't really helping anything. It's all kind of a mish-mash, with the color of the shadows on Cucumber (that little fella) not really matching the background. The whole effect is that he doesn't look like he's standing in the scene--just sorta floating. Like he's been poorly photoshopped in. :)
One last thing: now that I know this (fairly obvious) "secret," it's possible to (a) direct the eye better and (b)create some very dramatic mood. Like so!