Thinking about Medieval Murals

Image: Surviving lower half of the Refectory Mural in the Charterhouse, Coventry. Much of the mural is missing and part has been painted over with a coast of arms. You can see Christ's feet nailed to the cross, two men in armour and a women with a halo presumably Mary, mother of Christ.

What can surviving murals tell us about their original contexts? What are the limits of our powers of interpretation and reconstruction?