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.
Building a Chicken Coop - Recycled cans and little bit paint, so colorful and cute! Great idea for a little herb garden! Building a chicken coop does not have to be tricky nor does it have to set you back a ton of scratch.
Luminaries -- These are particularly great around the patio, or in a sitting space you’ve created out in the garden. Use tin coffee cans (or soup cans) and using a hammer and nail. Put citronella candles in these.