Think of the four different sons mentioned in the Haggadah:
The Wise Child
The "Bad" Child
The simple Child
The child who doesn't know how to ask
Maybe even read from the Haggadah who they were to familiarize yourself.
Now here comes the creative side, you are going to produce a representation of the Four sons. This could be four different faces characterizing the four different types of children. Or you can decide to take another angle and make an abstract model of something that represents each of the four children. At the Seder table others have to guess which object represents which son and why.