Hidden away in AutoCAD 2009's Options dialog box is an item labeled Color Scheme. Currently there are just two choices, Dark (default) and Light. But I see this as a skinning mechanism and perhaps programmers more knowledgeable than myself might be able to create additional skins.
How about an architectural skin that's all right-angles and looks like glass. Or a mechanical one that is all curvey and looks like metal. A geo one that combines fluorescent orange with earth tones.