After "bedtime," the nursery is always dark. We have a noise machine with a projector which provides enough light for feeding and diaper changes (possible exception of a messy poop, LOL). We don't really engage them beyond what is necessary for changing/feeding. The hope is they understand (on their level) this is sleep/quiet time and not play time. So far, it has worked for us.
We have twins in the same room, so we don't play in there during the day, either; there's just not enough space. When I was home, daytime activity was always downstairs. I don't know if that makes a difference or not...