We tend to view religion as a set of ideas that have been set in stone and is both everlasting and never changing. With this, nothing has been more lasting than the use of icons in Christianity, such as the use of stained glass windows that create colorful lights that splash across church walls, or the carvings of Jesus nailed to the cross, gazing in to the sky, seemingly in search of answers. This has not always been the case as Christendom has gone through periods of fierce iconoclasm.
The blue eyed, straight haired image of Jesus was once looked upon as being inherently against Christian values. In fact, all images were at one point seen as being against Christian values. During the fourth session of the Nicaean Council, a letter from Patriarch Germanos to John, Bishop of Synnada was read out loud. In the letter, John expressed that the use of iconography, in his opinion, was a form of idolatry.  The ideals behind the iconoclasm ideology comes from the Bible, “But the hour cometh and now is when the true worshipers shall worship the Gather in spirit and in truth.” (John 4:23)
There was doubt surrounding how Jesus looked, thus any representation of Jesus had the strong chance of being false. Placing incorrect pictures of Jesus in churches was a direct violation in the views of many church fathers. An even more clear cut damnation of idols comes from the Ten Commandments and the warning of creating “graven images” in God’s name. Spiritual worship rejected all forms of material aids including shrines, altars, and sacrificial victims. The Monophysite sect, which would later be declared a heretical movement, objected to all images and went as far to reject the depiction of angels as well. 
The use of icons, especially the portrayal of Jesus as a human, was insisted to be good practice at the Council of Trullo in 692.  Pictures were a good method for those who could not read to understand gospels and scripture; icons simply became an educational tool for those who were not taught the gospels through conventional means or a formal education. Despite the love and usefulness of these icons, the Byzantine Empire went through two phases of iconoclasm, in the years of 730-787 and 815-843.  Constantine V, who ruled from the 741-45, preached an iconoclasm that moved away from the veneration of painted wood. The only image of Christ was the Eucharist and the most sacred symbol was the cross. 
The military success of Constantine V meant that he left his son, Leo IV, a vastly stronger empire upon his death in 775. Forty years of iconoclastic policy under Leo IV ended upon his death and his teenage son, Constantine VI took the throne. There was one issue: Leo IV’s wife, Irene, was the protector of Constantine VI and was pro-icons. She would later call an Ecumenical Council meeting and invite all of the iconophiles that lived in exile under her late husband and his fathers reign. After the first meeting was broken up by iconoclastic bishops, they met again in Nicaea in 787 to come to the conclusion that images can be used in worship, even if worship is reserved for God alone.  Irene would call for all iconoclastic texts to be destroyed and when her son tried to rule on his own, she had him blinded. She would be the sole ruler of the Empire as icons took their place in Christianity.
It is important to understand Leo III and his anti-icon position and the nuances in the situation: Leo III and Yazid II, the Umayyad Caliph, both had iconoclastic policies at the same time. Although many sects in Islam have an anti-icon position, Christians living under Islamic rule were left alone in terms of iconography; Muslim clerics and rulers during this time had more issues with the crucifix than with the cross itself as the cross simply allowed for one to be identified as a Christian. This could come with various ideologies which Islam may reject, but tolerate, from a theological stand point.
For example, Arian Christians who did not believe in the Trinity would still use the cross as a symbol of the Christian faith. The crucifix, namely the image of Jesus being crucified, is a concept that Muslims object to with no ambiguity on what the symbol stood for. Leo III would not need Islam to form a position on iconoclasm, but it is interesting that both enacted the policy at the same time.
Theophanes, a historian, called Leo II, “Saracen minded,” or thinking like a Muslim, regarding the use of icons in 725.  Yazid would go further than his cousin and predecessor, Umar Abd al- Aziz, in terms of iconoclasm. What we do know is that Umar and Leo were in correspondence and did in fact, discuss the imagery of the cross. Leo says that while the cross is a symbol of honor and respect, lesser respect is shown to pictures. Umar himself did not destroy crosses, but would order that they be removed from public display in such places like Damascus. 
The public banning of crosses should not be seen as an Islamic tradition but as an Umayyad policy, which under Yazid II went a step further to the actual destruction of crosses.
What does all of this mean?
For me, the pictures of a white Jesus with straight hair and blue eyes, the Jesus that most people are familiar with, was not always revered and worshipped. Furthermore, I believe that theology is just as much political as it is spiritual. What we think as “always was” is in fact as a struggle that impacted both the Islamic and Christian worlds.
 G.E von Grunebaum, Byzantine and the Influence of the Islamic Environment, (Chicago, University of Chicago, 1962), p. 2
 Gruenbaum, Byzantine and the Influence of Islamic Environment, p. 5
 Judith Herrin, Byzantium: The Surprising Life of a Medevil Empire, (Princeton, Princeton University Press, 2007), p. 105
 Herrin, Byzantium, p. 106
 Herrin, Byzantium, p. 109
 Herrin, Byzantium, p. 111
 Grunebaum, Byzantine Iconoclasm, p. 2
 G.R.D. King, Islam, Iconoclasm, and the Declaration of Doctrine, (London, University of London, 1885), p. 269