The image here is from the article linked below, but the difference here is quite striking. The Van Eyck’s original lamb had a much more anthropomorphic face, and thus perhaps pointed more to the nature of the Lamb of Revelation 5 than the more naturalistic, overpainted lamb that we assumed was the original for so long. It definitely gives us something to think about with regard to the original intent for the altarpiece’s viewing.

Restoration of Ghent Altarpiece reveals surprising face on the “Lamb of God”