Mel [Gibson] isn't a theologian. But he is a devout artist. In the Pope's letter to Artists he speaks about art as a "genuine source of theology" because the devout artist in communion with God as beauty becomes a conduit of revelation. Mel doesn't necessarily understand all the nuances of the theology in his work. He is fleshing out an inspiration. It is the job of theologians now to step forward and interpret.
...at the end of the [Second Vatican] Council the Fathers addressed a greeting and an appeal to artists: "This world—they said—in which we live needs beauty in order not to sink into despair. Beauty, like truth, brings joy to the human heart and is that precious fruit which resists the erosion of time, which unites generations and enables them to be one in admiration!" ... Thanks also to the help of artists "the knowledge of God can be better revealed and the preaching of the Gospel can become clearer to the human mind." In this light, it comes as no surprise when Father Marie Dominique Chenu claims that the work of the historian of theology would be incomplete if he failed to give due attention to works of art, both literary and figurative, which are in their own way "not only aesthetic representations, but genuine 'sources' of theology."
Recognition of the human need for beauty -- and of his paintings as genuine sources of theology -- is why I chose to be known as John of Fiesole (Beato Angelico) in the [Third] Order of Preachers. (Nor does it come as a surprise that it's a Dominican the Pope quotes about the relationship between art and theology.)
Barb writes that Gibson "doesn't necessarily understand all the nuances of the theology in his work," but "is fleshing out an inspiration." I think the same is true, not just of religious artists, but of all artists. Maybe even of all workers.
We are created to communicate God to each other, and while it's dead easy to fail to do that, it's also not that hard to succeed -- since, after all, it's by God's grace that we succeed, which mostly requires us not actively hindering it. We can succeed even when neither we nor those we're communicating with have any explicit idea God is involved. He's sort of irrepressible that way.