I think it would be interesting to see how a really good outdoor lighting installation affected home value. It would probably have to be a higher end home in a higher end community. I don't know that lighting alone on a regular mid-range home in your average sub-division would really matter too much. But in nicer estates, I think it could add value - even add to sale value - because it's something that is more expected, or at least valued, in a home like that.
Probably also really depends on the area of the country. I know there are some areas I travel to (like Palm Springs, CA) where professional outdoor lighting seems to be standard on most homes. So it seems to be very highly valued in an area like that. While other areas like Portland, OR seem to not have a high percentage of homes with professional outdoor lighting. Which is nice because it's a wide-open market here. But it's also a harder sell because it's not as typical or valued unless you're in a really high end estate. Nevertheless, we seem to have finally hit a niche. Just this month alone we've sold 4 big lighting jobs.