We made the decision to keep the lighting very simple - it's top-left to match what is typical in user interfaces.
We could certainly put lighting control in there - the lighting renderer is very powerful and can support any number of lights in any colour - even lights that subtract colour from the scene.
But representing that in a simple way is quite daunting.
I've attached a lighting control we've used in other apps. You add a light, it's stuck on a pin to a textured ball, and you can move the lights around to see the effect.
But that might be overkill. Maybe just a couple of presets for warmth and direction would do. Who really wants lights that suck all the blue out of a scene?
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"