This essay is published in Christian Worship in Reformed Churches Past and Present, edited by Lukas Vischer (Grand Rapids, MI: Eerdmans, 2003). Here are a few concrete points I’ve taken away from it:
- If we want to engage the total person in the worship of God, we need to take into account the visual.
- Images are limited in their ability to reveal God, but so are words.
- Just because images have been used wrongly in church history doesn’t mean that we should reject them but rather should teach the church how to use them rightly. (The same principle applies to any good thing that is abused by the church.)
- For Christians, the image is not an end in itself.
- John Calvin acknowledged that from time to time Scripture speaks of God as giving definite, visible signs of his presence: for example, cloud and fire; a burning bush; a snake on a staff; a dove; etc. We need these signs that point to the mystery of God, and this is exactly what artists can give us.
- The Bible uses various anthropomorphisms for God—that is, it contains references to his mouth, ears, hands, and feet. These descriptions are nonliteral. So too are visual representations of God. The Bible is full of word pictures as well—for example, God as father, shepherd, physician, etc. If we allow for metaphors in verbal communication, why not in visual communication?
- Along this same line: Why are visual images of God sometimes considered dangerous/sinful but mental images are not?
- Baptism and communion are visual symbols instituted by Christ. They don’t convey the totality of the salvation experience but they convey it in part. We wouldn’t argue that God cannot be confined to bread and wine, or to a tub of water. So why would we say that a painting, for example, confines God?
- The visual artist may be an interpreter of biblical stories and images.
- Visual art may present aspects of the world for which the church is to intercede.
The Jesus Question 
It is unfortunate that the Protestant Church has forgotten the most compelling fact that would encourage us to use icons in worship: Jesus became a man. He could be looked at. This was not just a visible sign of his presence, as mentioned above, but in fact God has a face that humans can look at and worship. The tradition of iconography goes back to the beginning of the Church precisely because God became flesh in a way that could be represented with paint, and in making and venerating icons, Christians proclaim the reality of the Incarnation.
Good point! I actually meant to include the following line from the essay as a bullet point but apparently overlooked it: “The idea of the image of Christ as the image of the invisible God must be considered.” Protestants are real keen on embracing Jesus as the “Word” of God, but what of him being the “Image” of God?
I feel in general though that Christians are more open to seeing Jesus depicted than God the Father. Though I don’t have citations on hand, I have heard some pastors/theologians mention that the former is OK whereas the latter should be forbidden, because “God is a spirit,” and depicting him as an old man, as was common in medieval and Renaissance art–or in any human form, for that matter–is misleading.