Start with a blank canvas with some masking tape in the shape of a cross. Provide some paint and let people make their mark with finger painting or handprints.
Apart from looking really effective, it is a wonderful reminder that the death of Jesus makes it possible for us to be cleansed from sin (1 John 1.7-9).
No matter how messed up our lives are or what we have done, Jesus is willing to cleanse us and to offer us a new start. All we need to do is confess our sin to Jesus and call on him for forgiveness.
Jesus was willing to die to make it possible for us to be cleansed from our sin, which separates us from God. How amazing is that?