In the Orthodox Church the icons bear witness to the reality of God’s presence with us in the mystery of faith. The icons are not just human pictures or visual aids to contemplation and prayer. They are the witnesses of the presence of the Kingdom of God to us, and so of our own presence to the Kingdom of God in the Church. It is the Orthodox faith that icons are not only permissible, but are spiritually necessary because “the Word became flesh and dwelt among us” (Jn 1:14). Christ is truly man and, as man, truly the “icon of the invisible God” (Col 1:15; 1 Cor 11:7; 2 Cor 4:4).
The iconostasis or icon screen in the Orthodox Church exists to show our unity with Christ, his mother and all the angels and saints. It exists to show our unity with God. The altar table, which stands for the Banquet Table of the Kingdom of God, is placed behind the so-called royal gates, between the icons of the Theotokos and Child and the glorified Christ, showing that everything which happens to us in the Church happens in history between those “two comings” of Christ: between his coming as the Saviour born of Mary and. His coming at the end of the age as the King and the Judge.
The icons on the royal gates witness to the presence of Christ’s good news, the gospel of salvation. The four evangelists who recorded the gospels appear, and often also an icon of the Annunciation, the first proclamation of the gospel in the world. (In Greek the gospel is the evangelion, the authors of the gospels the evangelistoi, the annunciation the evangelismos).
Over the doors we have the icon of Christ’s Mystical Supper with his disciples, the icon of the central mystery of the Christian faith and the unity of the Church in the world. It is the visual witness that we too are partakers in the “marriage supper of the lamb” (Rev 19:9), that we too are blessed by Christ “to eat and drink at my table in my kingdom” (Lk 22:30), blessed to “eat bread in the Kingdom of God” (Lk 14:15).
Over and around the central gates are icons of the saints. The deacon’s doors in the first row (for the servants of the altar) usually have icons depicting deacons or angels, God’s servants. The first row also has an icon of the person or event in whose honor the given building is dedicated, along with other prominent saints or events. Depending on the size of the iconostasis, there may be rows of icons of the apostles, the major feasts of the Church, the prophets and other holy people blessed by God, all crowned on the top by the cross of Christ.
In recent centuries the iconostasis in most Orthodox churches became very ornate and developed into a virtual wall, dividing the faithful from the holy altar rather than uniting them with it. In recent years this development has happily been altered in many places. The iconostasis in many church buildings now gives first place to the icons themselves and has become once more an icon “stand” or “screen” (stasis) rather than a solid partition.
Besides the iconostasis, Orthodox Church buildings often have icons or frescoes on the walls and ceilings. The “canon” of Church design is to have the icon of Christ the Almighty in the center of the building, and the icon of the Theotokos with Christ appearing within her found over the altar area. This latter icon is called the “image of the Church” since Mary is herself the prototype of the entire assembly of believers in whom Christ must dwell. In the altar area it is also traditional to put icons of the saints who composed Church liturgies and hymns. Directly behind the altar table there is usually an image of Christ in glory—enthroned or transfigured or resurrecting, and sometimes offering the eucharistic gifts.
From:The Orthodox Faith by Fr. Thomas Hopko