My favorite kind of art project is one where the kids get to personalize it in their own special way. For this project I asked them what they were thankful for...(in a variety of ways so they would understand, because I know thankfulness can be a bit abstract for a preschooler.) The other preparations for this craft included cutting out leaf shapes from magazines and brown rectangles for the tree stump. Overall a very easy craft to make, and if you have older kids they could cut out their own leaves!
My favorite is the one that says, "Mommy, Daddy, God, Jesus, and Mickey Mouse" :)