Elf house on a tree! That would be cute in the garden, especially in the tree over grown with ivy. How about some battery tea lights in the windows during outdoor parties. I hear the fairies/elves whispering "home school project" in my ear.
Takanori Aiba is a Japanese artist who specializes in intricate Bonsai Tree-houses. Aiba uses craft paper, plastic, plaster, acrylic resin, paint and other materials to construct sprawling miniature tree-house communities that wrap around bonsai trees.
Another version on rain gutter gardening. Want to grow a salad garden but have no room? Try gutters! Affix them to a fence, slope them for drainage, and voila! Of course,for this I'd need a backyard wider than a hallway.