That's a very creative idea! You can definitely make a Christmas tree out of a tomato cage, but it may take a little bit of work. First, you'll need to find a tomato cage with the right shape and size for the tree you want to make. Then, you'll need to wrap it in lights and decorations to give it that festive look. Finally, you'll need to find a way to secure it in the ground, so it doesn't blow away in the wind.