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.
Unique DIY String Light Poles with Concrete Base. These DIY string light poles are extra sturdy and they look unlike any string light poles we’ve seen, with tree trunks taking the place of wooden or metal poles in the concrete bases.
Clever idea from my husband: Steps to tree stump fairy garden made from tree limb coins/wedges, with a nail hammered into side, nail head cut off, then hammered into side of tree stump. - Gardening And Living - Fairy Gardens
Log Bird Feeder - 23 DIY Birdfeeders That Will Fill Your Garden With Birds (my note: I haven't looked at all of these, but at least one is a terrible idea. The window birdfeeder -- birds could fly into the glass and hurt themselves.