Shelving may be one of the easier DIYs to take on. You could build your own fabric shelves, any number of forward facing shelves, or even a truck shelf. But if you've got an airplane-themed kids' room, you might want to try making this bi-plane bookshelf.
Since the instructions for this project call for raw lumber, you could build your shelf to any size for any age child. This version is for a nursery, so the shelves aren't that deep, but for an older child you could build out the shelf width. We love the pilot seat, which is perfect for a favorite stuffed animal.
(Images: Remove and Replace)