God commands the Israelites not to make carved images (Exodus 20:4), but also commands the Israelites to carve images of cherubim on the Ark (Exodus 25). This would appear to be contradictory. However if you read the context of the command, it seems that God is not forbidding images of any sort but forbidding images that are worshipped. “You shall not bow down to them or serve them” (Exodus 20:5).
The cherubim do seem to have been there as a visible sign of God’s presence among them. He said he would meet with Israel there, at the ark, and would speak “from between the two cherubim that are on the ark of the testimony”. (Exodus 25:22). When establishing the commands for the Day of Atonement, God said he would “appear in the cloud over the mercy seat” (Leviticus 16:2). Being “enthroned on the cherubim” is a title which is applied to God in a number of places as a part of praise and worship of his greatness (e.g. Psalm 80:1; Psalm 99:1; Isaiah 37:16). So obviously the image does have some importance.
However, I think something relevant about the cherubim on the ark is that they were not actually to be seen by the people of Israel, just by God’s chosen representatives. While the people of Israel could have worshipped them, it would only have been by hearsay (unlike the Golden Calf, for example).
The ark of the covenant was to be kept in the Most Holy Place of the tabernacle (and afterwards the temple), and only the high priest went in there once a year on the Day of Atonement, following a carefully prescribed ritual (Leviticus 15). This was very important so that the priests would not be killed by the presence of God.
In the wilderness when the ark was carried it was meant to be carefully covered by the priests (Numbers 4:5 – 6). Even looking at the holy things for a moment could lead to death (Numbers 4:17 – 20). In short the cherubim were not intended to be an image visible to the people or even the priests (though it doesn’t seem these commands were completely followed , and as a result some died after looking into the ark in 1 Samuel 6:19).