Rice paper lanterns are a cheap way to decorate your terrace. I bought three green and three turquoise ones from Indiska a couple of summers ago and they cost around 2 euros each. If you keep the lanterns under a roof and take them inside for the worst of weather they will delight you for many years. I haven´t put any lamps in these, I think they are decorative enough just as they are. And in any case it is so light in summer evenings it would be more trouble than use to provide the lanterns with electricity. If you like more subtle decoration, choose the classic white ones.