What makes an icon different from other artist's renditions of Biblical stories or Biblical personages, such as the Last Supper or pictures in a children's Bible?
I don't think you realize what a huge topic this actually is. This is something I put together a few years ago after reading a few books on icons. Hopefully it will answer your question.
The earliest iconographers in Byzantium weren't considered artists they were considered craftsmen. There are strict rules to iconography. God the Father is never shown, and the Holy Spirit is only represented by a dove, rays of power, or tongues of flame. People who defile them, make portraits of other people like Ghandi or Martin Luther King in an iconographic style, people who print them on t-shirts: it is seen pretty much as very sad and outrageous. Not everything that claims to be an icon is an icon. Books upon books have been written about icons. I suggest to anyone interested in the subject to go find some books (I especially rec Quinot and Martin).
Medieval innovations of using models to paint sensual and emotional portraits is absolutely forbidden.
Linette Martin in her book
Sacred Doorways: A Beginner's Guide to Icons (page 212) states, "To the question,'Where does an icon belong?'; the obvious answer is, "In a church, to be an integral part of the Divine Liturgy, or in a Christian home as a devotional focus."
Symbolism is key. There is a lot of it to be found. From seemingly random trees, to personification, to color, to the way figures hold their hands, to the scale of figures, to profiles, animals, arrested movement, body language, buildings, clothing worn, drapery, rocks, furniture, haloes, handheld objects, inscriptions, landscape, simultaneous narration, etc. it all means something. There is an entire theology behind icons.
The earliest icons we know of are almost all at St. Catherine's Monastery in Mt. Sinai, Egypt (and many of them were exhibited at the Getty for a few years ago, accompanied by a few of the Monks). Go to their website and watch the video about the monastery and the icons.
http://www.getty.edu/art/exhibitions/icons_sinai/
The following is an excerpt from an article that gives an extremely brief general overview of icons. I highlighted the last paragraph because it talks specifically about Christ in icons. (Seriously- read the entire text box.)
Eastern Orthodox Christians and Iconography | Antiochian Orthodox Christian Archdiocese
So what is an icon? Webster defines an icon as an image (Webster, 1966). In the Orthodox Church an icon is a sacred image, a window into heaven. An image of another reality, of a person, time and place that is more real than here and now. More than art, icons have an important spiritual role. Michel Quenot says it well in his book, The Icon: Window on the Kingdom, an icon is "theology in imagery, the icon expresses through color what the Gospel proclaims in words".
For this reason the rules regarding the creation of an icon are rigorous. The iconographer must prepare himself for the task of painting an icon by following a strict discipline of fasting and prayer. He must quiet his spirit and submit himself to God. The icon he creates will not be signed. He will not expect accolades or applause when the icon is completed. The icon will be created to inspire and lead others into worship. Painting the icon is not a use of imagination. Instead, the icon will be painted using the prescribed regimen and style that has been passed down through the centuries. Everything from the facial expressions to the colors used is predetermined. The following is a prayer recited by an iconographer prior to starting to work:
O Divine Master of all that exists, enlighten and direct the soul, the heart and the mind of your servant: guide my hands so that I might portray worthily and perfectly Your Image, that of Your Holy Mother and of all the Saints, for the glory, the joy, and the beautification of Your Holy Church. ( Quenot, p.13)
The primary purpose of the icon is to aid in worship. Its design follows that purpose. Through lines and color the iconographer conveys the awesomeness of the invisible, divine reality (Evdokimov, 1990). The creation of an icon is defined by tradition. That is a 21 st century iconographer would not decide to change the shape of Christ's face. It is understood that a person who saw them in the flesh painted the first icon of an individual. St. Luke is accredited with painting the first icons of Christ and Mary the Blessed Virgin. Each subsequent iconographer will use the original icon as a guide. There is room for a small amount of stylistic change but tradition limits the options for that change ( Forest, 1997).
Icons are not created to force an emotional response. When portraying historical scenes the faces don't show emotions but instead portray virtues such as purity, patience in suffering, forgiveness, compassion and love. An example of this would be the portrayal of Christ on the cross. Neither is the icon a sentimental picture. Christ is always shown as God. Even the icons of Christ seated on His mother's lap show Him with an adult face, revealing that even though Christ lived as a child among us He was also God ( Forest,1997).
Icons depict silence. There are no actions displayed, no open mouths. The icon invites the Christian to enter into contemplation,prayer, and silence (Ware,1979). Space is not defined as three-dimensional and time is insignificant. The story told by the icon precludes time and space. An example would be the icon of the Nativity, which shows the cave where Christ was born in the background with those who came to adore in small vignettes. Lighting proceeds from the character portrayed in the icon. There are never shadows in icons. This shows us that the saint portrayed is 'glorified' having completed the race and entered into heaven (Quenot,1991).
Symbolism is used in icons and details are used minimally. For example, when showing John the Baptist baptizing in the river the grown man he baptizes is shown as an infant because the baptism is a rebirth. Colors are also symbolic. Blue reveals heaven and mystery. Green is youth, fertility and the earth's vegetation. Red, the color of blood, suggests life, vitality and beauty. White is purity, the divine world and innocence. Gold indicates sanctity, splendor, and the glory of God and life in the heavenly kingdom. Purple reveals wealth, power and authority.
First and foremost, icons are a constant reminder of the incarnation of Christ, that is to say, they remind us that God "sent His only begotten Son" (Bible, John 3:16) to rescue us from our sin and death. We cannot see God the Father or God the Holy Spirit, but, because Christ chose to take on human flesh, we can see Him. His face can be portrayed on wood with paint. We can also paint His Mother and other saints who have finished the race and gone on to heaven. The Orthodox believe that surrounding themselves with icons help them to acknowledge the constant presence of Christ and the saints in their lives.
I thought this was enlightening enough regarding the particular thread to add in this information about how Christ is portrayed in icons.
From Linette Martin's book,
Sacred Doorways: A Beginner's Guide to Icons (pages 150-151) published by Paraclete Press, copyright 2002:
"Christ Pantocrator (pan-to-crah-tor) means Christ, the ruler of all.
"The domed roof of a Byzantine church represents the vault of heaven, and originally, mosaicists may have decorated it with the Ascension. By the tenth century, the figure in church domes was half-length, and the picture for a dome had changed from narrative to confrontational. It was discovered that a half-length figure fitted more easily into a circle than one of full length, and it allowed the face to be on a larger scale. He holds a closed book, which may be seen as the Gospels or as the Book of Judgment in
Revelation 20:11,12
"The fingers of his right hand are bent in the position of a priest's hand of blessing and are pointing toward himself. The index finger of his other hand points powerfully across the picture, balancing the sideways glance of his eyes to his left. When we look carefully at the face of this Pantocrator, we see a difference between one side and the other. His right side, the side of blessing, is calm; his left side, the side of judgment, is fierce with an angry eyebrow. After nearly nine hundred years this awe-inspiring image still has the power to convert. Confronted with it for the first time some people react with shock: This is not a tame Jesus. The only thing that lets us off the hook is that those eyes do not look directly at us. The image is a reminder that the Last Judgment should be feared because it will be absolutely just, albeit tempered by mercy and total understanding.
"The Pantocrator is not intended to represent Christ as the Jesus of Galilee, but as the awe-inspiring God-Man, the King of the Universe and terrible Judge at the end of time."