Well, sounds are really distracting, but light isn't so bad. Sleeping in light can actually be easier for some people.

As for light's effect on lucid dreams, I'd say that it makes your dreams literally brighter! From experience, the few dreams I do remember are commonly dreamt in the daytime, and thus the dreams are also in day. When I DO dream at night, the dreams are in the night. Hmmm, maybe that could be worked into a dreamsign? Still, I dunno if everybody gets this effect. I'm really aware of my body while I'm sleeping, so I dunno.