Battery-powered white paper lanterns saved our wedding reception. It was held outdoors in a Point Reyes Station garden patio and, being city folk, we hadn't anticipated just how dark it would be after nightfall. The night before the wedding we tested out the existing garden lights and atmospheric table candles and realized that together they would provide just enough light to keep our guests from falling asleep.
A friend of ours brought some backup lights in the form of charming, battery-powered white Chinese lanterns in various sizes. Like X-mas tree ornaments they came with hooks, and we used these to festoon the bushes and trees around the patio's perimeter. At sunset our siblings went around and ritually flicked the switch on each lantern individually. It was a brilliant and lovely-to-behold solution, requiring no power cabling and no stress.
You can also make any 10" or larger paper or nylon lantern you make or buy into a battery-powered light with the help of a $2.35 hanging battery terminal.
If you like to entertain outdoors at night, it's good to have some of these hassle-free illuminators on hand. They typically use 2 AA batteries and a small candelabra bulb with a burn time of 5 - 7 hours per battery set.
(Edited from a post published 06.22.07 - CB)