During the recent discussion on images of God, I have heard a couple of folks suggest that God portrayed himself as being a pillar of cloud and fire.
A more careful reading of the text shows that while the pillar of cloud/fire was a sign of the presence of God, it was not supposed to represent God. Instead God was "in" the pillar:
Exodus 13:21 And the LORD went before them by day in a pillar of a cloud, to lead them the way; and by night in a pillar of fire, to give them light; to go by day and night:
It was something that God provided to the people of Israel:
Exodus 13:22 He took not away the pillar of the cloud by day, nor the pillar of fire by night, from before the people.
Psa 105:39 He spread a cloud for a covering; and fire to give light in the night.
When God stirred up the Egyptians he is described as doing so "through the pillar," as though God were within the pillar, hidden.
Exodus 14:24 And it came to pass, that in the morning watch the LORD looked unto the host of the Egyptians through the pillar of fire and of the cloud, and troubled the host of the Egyptians,
As an aside, we may note that the same distinction exists with respect to the burning bush. The angel of the Lord was not the burning bush, but spoke out of it.
Exodus 3:2 And the angel of the LORD appeared unto him in a flame of fire out of the midst of a bush: and he looked, and, behold, the bush burned with fire, and the bush was not consumed.
When the tabernacle was built, this special manifestation of God's presence was placed on the tabernacle itself:
And on the day that the tabernacle was reared up the cloud covered the tabernacle, namely, the tent of the testimony: and at even there was upon the tabernacle as it were the appearance of fire, until the morning. So it was alway: the cloud covered it by day, and the appearance of fire by night.
Exodus 40:38 For the cloud of the LORD was upon the tabernacle by day, and fire was on it by night, in the sight of all the house of Israel, throughout all their journeys.
And when God led the people he led them with the pillar:
Deuteronomy 1:33 Who went in the way before you, to search you out a place to pitch your tents in, in fire by night, to shew you by what way ye should go, and in a cloud by day.
Psalm 78:14 In the daytime also he led them with a cloud, and all the night with a light of fire.
Nehemiah 9:19 Yet thou in thy manifold mercies forsookest them not in the wilderness: the pillar of the cloud departed not from them by day, to lead them in the way; neither the pillar of fire by night, to shew them light, and the way wherein they should go.
The pillar of fire and smoke became a renowned sign among the Canaanites, much like the story of the Exodus.
Numbers 14:14 And they will tell it to the inhabitants of this land: for they have heard that thou LORD art among this people, that thou LORD art seen face to face, and that thy cloud standeth over them, and that thou goest before them, by day time in a pillar of a cloud, and in a pillar of fire by night.
It's worth noting that when God specifically disclaims the fire as a similitude of himself (as if the distinctions we had drawn above were not enough):
Deuteronomy 4:12 And the LORD spake unto you out of the midst of the fire: ye heard the voice of the words, but saw no similitude; only ye heard a voice.
And likewise, by connection with the other manifestations (by connection) we can infer that they were also not intended as similitudes:
Deuteronomy 5:22 These words the LORD spake unto all your assembly in the mount out of the midst of the fire, of the cloud, and of the thick darkness, with a great voice: and he added no more. And he wrote them in two tables of stone, and delivered them unto me.
That ought to pretty much close the case against the pillar and cloud being representations of God. Since the pillar of cloud and fire are not representations of God, Christian artists should not feel concerned about drawing the imagined pillar.
As an interesting aside, the pillar of cloud and fire makes one additional appearance in the Old Testament. Pointing toward the new covenant, Isaiah describes this sign of God's presence as being upon every dwelling place of mount Zion (i.e. the individual believers and their households), and the assemblies (congregations or churches).
Isaiah 4:5 And the LORD will create upon every dwelling place of mount Zion, and upon her assemblies, a cloud and smoke by day, and the shining of a flaming fire by night: for upon all the glory shall be a defence.
There is not, of course, a literal smoke and cloud pillar that goes up from our houses and churches, but God is present invisibly with us. If we wish to be wise we will worship God not with the works of men's hands, but in Spirit and Truth, as it is written:
But the hour cometh, and now is, when the true worshippers shall worship the Father in spirit and in truth: for the Father seeketh such to worship him. God is a Spirit: and they that worship him must worship him in spirit and in truth.