The Warburg Method teaches us that devotional art is not only not always beautiful, but rarely beautiful -- because it is deeply coded and the untutored eye doesn't always get it. Is not intended to get it. This is true across civilizations, not just true in the Western painting tradition.
As the blogger knows, his stock represents about 400 years of devotional painting, in the Byzantine as well as Western traditions. This is interesting not because it makes his blog title inaccurate but because it's a crash course in how observation-based painting changes things, and in how it doesn't.
Does it matter if the painter is going for naturalism? This is something no Byzantine painter ever heard of doing. A Virgin enthroned on a huge wall 30 feet up from where the viewer stands is not meant to look like a sweet British mom wondering at the miracle of her rosy child. The heavy dark lines describing the faces are meant to suggest modeling and somberness from a great distance, in candlelight. The wall painter of any era knows -- the image must read. If you look at what the painter has done up close, in a book or in a photo blog, you miss that point and see only a coarse, hirsute appearance, one that seems inexplicable and uglified. The somberness and linear quality of Byzantine images is present in hand held icons too, but these are more delicately painted. What you will never see is a Byzantine genre scene -- painting was for depicting holiness. To be holy is to be set apart, and to look it. If you notice, the Buddha is never represented as a conventionally handsome South Asian man -- other stuff is going on in those representations, as it is in the way Byzantine painters represented holy men, women and babies.
There are eras in painting where you would find only Madonna and Child images that speak of what an agonizing fate it is, to be the Son of God, and how grave and sorrowful His mother must be. There are other eras wherein the cult of the Holy Infant took a different turn, the art focusing on the deep joys of Christianity, on the life the Christian is given that is as new and as disburdened as an infant's life. Virgin and child are emblematic of perfect trust, even in the presence of great foreboding. If, as a painter, you mean The Awful never to be very far away, you will have your ways of demonstrating that. Christ is not "a guy like you," and the most strangely powerful images of Christ are intended to show the viewer the aspect of Christ that he can empathize with -- the Christ who is set apart, and bears about himself even in infancy the traces of an unendurable but splendidly meaningful life. What woman can be sadder than the Madonna, yet more convinced of her unique significance? Should she not occasionally look the part? A huge if not often explicated purpose of devotional art is to give courage to the devotee; images of extreme conventionality may fail in this aim.
Well, I am NOT an authority, only a lifelong student and reader, with a (very) distant degree in Art History. But! The observation of children _as_ children, not as trainee adults who need to be fit to enter the labor force ASAP, is a moder...n phenomenon, in art and in literature. With that shift in focus comes all kinds of romanticizing: the savage, the angel, the superb victim, the young hero, and so on, with many of these categories overlapping or morphing into one another. Restricting myself to art, I want to point out that observation based painting and drawing is modern, as in Renaissance and Post-Ren., the Greeks and Romans being another subject. It was against Church and other laws to learn anatomy via dissection, and even Michelangelo risked much when he learned anatomy from corpses, so this left the art of the Middle Ages, and Byzantine art, as well as the art of the Early Renaissance, at a certain powerful disadvantage, IF good art is supposed to look like what you see with your eyes, not your inner eye. An important part of learning about art, of having the full experience of art, is to allow your own inner eye to magnify what is deep and true in many forms of expression, over many stylistic conventions. I am not the world's biggest fan of Byzantine holy images, for instance, but not liking them on the grounds of their being stylized, static, and a failure at resembling human beings is like thinking Haiku might be better if it were longer. And, yes! In any era, if an artist needed to take a wife away from her labors to "sit in" for a missing Madonna, or to borrow a toddler for John the Baptist or an infant for Christ, you may be sure it was over very quickly!