The Icon of this feast has baffled me for a long time and I've never been able to figure it out, but thank goodness there are wiser people out there in the blogosphere who have access to knowledge which I lack. The following is an explanation of the icon of Pentecost and how the Eastern depiction differs from depictions in the west.
This explanation is taken from the book The Meaning of Icons by Vladimir Lossky and reprinted on the website Mystagogy.
The Eastern icon representing the Great Feast of Pentecost is probably unfamiliar to most Westerners. In the Western painting tradition, the tongues of fire and the presence of the Holy Mother of God are emphasized along with, of course, the twelve apostles. At times, depending on the artist and style of the period in which the work was created, the scene can be quite animated with gesticulating figures and a composition suggesting confusion or wonderment. Excitement may seem to permeate the atmosphere.
In the Eastern tradition, icons of the Pentecost don’t always depict tongues of fire. Instead, at the top of the icon a circle or semicircle represents heaven and from its center, twelve rays point downward toward the twelve apostles, symbolizing the descent of the Holy Spirit.
Also, absent from the scene (in many Eastern icons) is the All-Holy Mother of God which is strange because the Acts of the Apostles makes a point of telling she was present. Such a glaring omission begs for an explanation. Here it is: The Pentecost icons of the Eastern Church, unlike the images of the event in the Western Church, stress the underlying ecclesiological meaning of Pentecost and less so the narrative details of the descent of the Spirit or observable physical facts, as reported in Acts.Along the same lines, in the icon at the bottom of (many) Eastern icons, is an image of something not reported in Acts. It appears to be a tomb with a king standing in the blackness of the interior. He holds a white cloth supporting twelve written scrolls. The king actually personifies the great multitude of people gathered in Jerusalem for the holy day. The image is called “Cosmos” and the dark place in which the king stands represents the whole world which had formally been without faith and had suffered under the weight of Adam’s sin. The red garment the king wears symbolizes pagan or the devil’s blood sacrifices, and the crown he wears signifies sin which ruled the world. The white cloth and twelve scrolls symbolize the twelve apostles who brought Christ’s light to the world through their teaching.
That is the core message of the Eastern depiction of Pentecost. The message is not so much about the physical manifestations of the descent of Holy Spirit as it is the substantial presence of the Spirit in the Church, acting through the Church, to sanctify the world. The Ascension of the Lord represented the end of Christ’s earthly mission and Pentecost represented the beginning of the residency of the Holy Spirit in the Church.
Rather than a general disturbance - often portrayed in Western images of Pentecost - caused by the descent of the Spirit, Eastern icons of the event express an overall sense of order, calm and solemnity. Here we see the unity and singleness of purpose of the hierarchic Church in converting the world. A formal arrangement of the apostles in a semi-circle surrounding the tomb and king is broken only by an empty space in the seating arrangement at the top of the bend. It is the seat reserved for Christ, the head of the Church. On close inspection, you will notice that the apostles are depicted in inverse perspective: the size of the figures grow bigger the closer they are to the seat reserved for Christ. St. Peter sits to the right (our left) and St. Paul, to the left (our right). St. Paul, of course, was not present at Pentecost, but that fact is not relevant here where the meaning of the icon is the substantial presence of the Spirit in the institutional Church. Actually, there are a few others also represented here who were not of the original twelve apostles: Luke the Evangelist (third from the top on the left) and Mark the Evangelist (third from the top on the right). They hold their gospel books. Paul also holds a book, symbolizing his letters. Others hold scrolls, symbols of having received the gift of teaching.
Contrasting with the uniformity of the semi-circle, and in harmony with the hierarchic detail, are the variety of poses in the figures of the apostles. No two figures strike the same pose. This goes to the inner meaning of the icon: although there is the one Spirit - one Body - each member is given special gifts.
As liturgical art, icons open a door for the worshiper into a transfigured world and into an experience of sacred time. An icon compresses events into one image and folds time into a holy present in order to communicate an inner meaning. It all comes together in this icon to show us the divine guidance given to the hierarchic Church in the conversion of the world.