Pope Benedict, in his preaching and teaching, has often stressed the importance of images to convey the Good News of our redemption. In the Compendium of the Catechism of the Catholic Church, which he oversaw as Cardinal Ratzinger, he stipulated that it contain a variety of images, both classical and modern, that illustrate the mysteries of the faith. They are, in my view, wonderfully effective.Monsignor Timothy Verdon is an American by birth, but has lived in Italy for thirty years, and is the director of the Office of Catechetics through Art of the Archdiocese of Florence. He has written numerous studies of the art of the Renaissance, and has composed commentaries on the liturgical year, using great works of art to "exegete" the Sunday readings.Recently he has reflected upon Leonardo Da Vinci's "Last Supper," placing it within its lived setting of the refectory of the Dominican convent of Santa Maria delle Grazie. Here is part of his exposition:

During the years [when] Leonardo painted the Last Supper, a Milanese artist, Donato Montorfano, frescoed the wall facing it with a monumental Crucifixion, which can still be seen at the other side of the room. As a result, after washing their hands with faith in the divine mercy, the friars who went into the refectory found themselves embraced by this mercy from both sides: in front of and behind them, there were images of the "great redemption" that Christ accomplished on behalf of sinners. On one of the two back walls they saw, in [Leonardo's] Last Supper, Jesus' dedication in offering his body and blood "for the remission of sins," and on the opposite wall, they saw in the Crucifixion the fulfillment of this dedication, when Christ offered his life physically on the cross. Having noted the need for forgiveness, the Friars therefore went to the table between the two moments in which this forgiveness had been realized: between Thursday evening and Friday afternoon of the "hour" of Jesus, between the Supper and the Cross.

The full text is here.