Getting the colors / values right; I may have to consider what to do about the shadows... maybe dim their alpha in the dark? I know I'll be lowering the light intensity from the campfire during the daytime (it looks like a flare now), but it's a start.
I could do shadow animations, (which sounds like a pain). I could also put in primitive shapes off the base and use some of the Unity asset store tools to have dynamic shadows... buuut most likely I'll just do an alpha fade on the shadow layer when it gets dark out.
Anyway, I'll just get the sunset / sunrise cycles going for now.