Wow, what fantastic replies! I can't thank you all enough for the info. I'd never even heard of Vray before, but I like the idea of checking several different versions out. (I'd never heard of photosculpt either, but that is just plain wicked cool.) Unfortunately, my laptop is definitely NOT built for fast rendering-I had no idea I'd get into this when I bought it-but I guess that's why you can leave it on overnight.
Right now, just based on replies, I'm leaning towards Twilight. That museum is exactly what I had in mind for my model. But I'll try a few of them and see what works best. Again, thanks so much!