Cherubim are spiritual beings mentioned frequently in the Old Testament and once in the New Testament. They were commonly used of those heavenly spirits, who closely surrounded the Majesty of God and paid Him service.
In Moses' Tabernacle and Solomon's Temple, cherubim are sculptured, engraved, and embroidered figures used in the furniture and ornamentation:
The fact that the Bible nowhere explains how the cherubim looked like, but always presupposes them well-known, makes us believe that they were among the most common figures of contemporary art in Ancient Near East. In Egyptian art, figures with a human face and two outstretched wings attached to the arms are exceedingly common. Two winged sphinxes also appeared frequently in Phoenician art and Assyrian art.
Thus today's Biblical scholars have suggested that cherubim are "similar to the statues of winged, human-headed bulls or lions that stood guard at the entrances to palaces and temples in ancient Mesopotamia." (from the NIV Study Bible, the commentary on Genesis 3:24).
The 3D model below shows the cherubim standing inside the Most Holy Place in Solomon's Temple.
Before we move on to discuss the appearance of the cherubim as seen by Ezekiel, we need to understand that the book of Ezekiel is highly symbolic:
Ezekiel described the cherubim in his vision as:
Ezekiel 1:5-11 (NASB)
5 Within it there were figures resembling four living beings. And this was their appearance: they had human form. 6 Each of them had four faces and four wings. 7 Their legs were straight and their feet were like a calf's hoof, and they gleamed like burnished bronze. 8 Under their wings on their four sides were human hands. As for the faces and wings of the four of them, 9 their wings touched one another; their faces did not turn when they moved, each went straight forward. 10 As for the form of their faces, each had the face of a man; all four had the face of a lion on the right and the face of a bull on the left, and all four had the face of an eagle. 11 Such were their faces. Their wings were spread out above; each had two touching another being, and two covering their bodies.
There are three reasons why we did not model the cherubim after Ezekiel's vision:
Some have used the description of the cherubim by Ezekiel in their model of the Solomon's Temple as shown below:

Ark work by Rodney Treadway, rtreadway11@verizon.net, used by permission
For more 3D images of the Temple modeled by Rodney Treadway, visit his web site at http://mysite.verizon.net/vzeu2swg/.
New Advent, "Cherubim", http://www.newadvent.org/cathen/03646c.htm.
Walter Reinhold Warttig Mattfield y de la Torre, "The Pre-Biblical Origins of Cherubim (And The Mercy Seat Atop the Ark of the Covenant)" http://www.bibleorigins.net/CherubimOrigins.html.
NIV Study Bible