Jacques Ellul argues, roughly, in his Humiliation of the Word for careful attention between the differences between the word and the image. The word has a kind of temporality and indeterminacy about it that demands presence and locality. Someone speaks and we either hear or we don't hear, it happens and then it is gone. It has potency, but a floating kind. The word strikes and then disappears. If one misses it, the moment is gone. A spoken word can be remembered or repeated, but this is a representation of a phenomenon that has passed.
For Ellul, the written word is not the same as the spoken word, and it in fact has more in common with the image. The written word and image seeks to engrave a certain moment, a freeze-frame of what was indeterminate. The word has potency, but also a mortality. It goes away, it can't be controlled, but its meaning flutters. The image or written enacts a kind of freezing upon life. It has now been rendered in such a way that the word or image can be assessed and examined. Some Post-Modernists find this as an incredible act of ontological violence, but I think that's stupid. Even if it is violent (which I doubt), that doesn't therefore prove that it is somehow immoral or evil.
However, Ellul's point is to show how this is dangerous. Trying to clamp down on the power of the word and freeze it can lead to the misappropriation of it for all sorts of reasons. This, he argues, was part of the reason behind numerous radical Reformers' insistence on destroying statues and stained-glass. They took the 2nd Commandment to heart and feared the power inherent in freezing the Word of God into many times erroneous images that threatened to distort the pure Word of God.
Yet I think these same arguments can be proof for the use of images in Christian life. Ellul's construction of the Reformation is a weariness of freezing images of God. One might reflect on this when one sees the purveyance of stupid bumper-stickers and refrigerator magnets (among many other media) quoting Bible cliches, many times devoid of context or sobriety. I think of Thomas Kincaid as a symptom of this abuse of the engraved word, namely turning the Word of God for the wistfulness of a fantasy. Kincaid's own struggle with alcoholism only compounds how Christianity, for him, became an escapism from the difficulties of life. Christ is blasphemed, and Feurbach proved, through the success of these men and women.
However, the problem is the danger of abuse, but not the abstention of use. If the engraved word is more akin to an image than the spoken word, then we see in Scriptural practice the presence of God in His mighty works for His people. We see God both present and absent, in how He speaks to Moses out of a Cloud. There is significance to how God gives Moses His name, which is not a name at all, but the illuminating darkness of blinding light. Moses can never know God except indirectly, this was not a claim that God was Being (contra. Thomas), but that God may be met in all being. The later Jews who changed the name of God to, literally, Name (HaShem) was perhaps superstitious, but it was ground in an understanding of what happened in Scripture. But I'd rather trust Moses' account, namely that what was written down, "Yahweh", was a name of God, but a nameless name. Considering the word was engraved, it was not blasphemous to say or use it, because it itself is a cover for the Glory of God.
However, in the Incarnation of Christ, we are given not only the name of God's Son, delivered by the Angel Gabriel, but we see the power of the Name. The Power of the Name Jesus is simultaneously Human and Divine, it is the direct power and presence of God, the full presence in the work of God completing the fullness of times. Speaking with the Apostles, we can say that Jesus is the Divine Name by which all of Creation, all of mankind, is saved; there is no other. In the advent of the Messiah, the promised Divine presence of God with His people, eternalized in His Ascension and Reigning as a Man, God's Word assuming Human Nature, we see God granting a kind of Iconic presence viz. speaking the word. When we say Jesus Christ, this is a great power and privilege (and misusing this name, more so than other phrases, like God or Lord or whatever people cuss by, is truly blasphemous). When we speak the name we call to bear a representation of the Real, Who is, by Nature, the Immaculate Image of the Father of All Lights.
Ideally, the icon is saying the word with color. It is a representation of the very same Real. It does not intend to depict physical description, but, like a word, communicates truth. This is why icons of the saints in Eastern iconography all look the same, looking similar to the iconography of Christ, namely that what is displayed is the same holiness. Since we are given the power and privilege of speaking the name of Christ, even risking the abuse of the Only Name under Heaven by which we are saved, we may speak such through the icon, though it might also be an opportunity for blasphemy (think of Buddy Jesus).
This is a tentative idea, but worth pondering. This does not prove any one instance or practice, but is a framework for assessment. The written word, as the image, is an opportunity for great risk. But, as many early synagogues show, numbers of Jews did not see a problem with mosaics of creation and the saints as a part of their worship environment. However, we need to see this within the context of the 2nd Commandment and the sins of worshiping in High Places. What these mean, in conjunction with the above, should be included in any discussion about the uses of visual images in Christian worship.
Addendum: It should be obvious, but the Lord's Supper and Baptism, utilizing the meaning conduits of matter, namely water, bread, and wine, fits this representational form. In these, God's Spirit actually transforms us and the elements into Communion with Christ, where we partake of His flesh and blood. This is absolutely necessary, and thus somewhat out of the parameters of our argument. In Christ Jesus, we are a given a name we can speak. Christians are not limited, in literalistic fashion, to the mere text of Scripture in speaking of God. What I mean is that no Christian has seen a problem in writing about doctrine or offering sermons that are not verbatim from the Bible, even if they are wholly, or in part, derived from Biblical concepts and formula. The icon falls under this discussion.