Image Idolatry

The pathos of the crucifix obscures the glory of Christ, for it hides the fact of His deity, His victory on the cross, and His present kingdom.  It displays His human weakness, but it conceals His divine strength; it depicts the reality of His pain, but keeps out of our sight the reality of His joy and His power.  In both these cases, the symbol is unworthy most of all because of what it fails to display.  And so are all other visible representations of Deity. …

Psychologically, it is certain that if you habitually focus your thoughts on an image or picture of the One to whom you are going to pray, you will come to think of Him, and pray to Him, as the image represents Him.  Thus you will in  this sense “bow down” and “worship” your image; and to the extent to which the image fails to tell the truth about God, to that extent you will fail to worship God in truth.  That is why God forbids you and me to make use of images and pictures in worship.

J.I. Packer, Knowing God, pp.41-42