While the use of human heads as crests was very popular from the earliest rolls, their use as charges on shields came later, as in the arms of Gundelsdorf, c.1340 [Zurich 431]. Some human heads are affronty or guardant by default, but others aren’t; it depends on the type of human. As a general rule of thumb, men (Saracens, blackamoors, &c) face dexter by default, while children, maidens, &c, are affronty.
The “savage’s head” and the “wild man’s head” are shown with a wreath of leaves on their heads, since the leaves on the rest of their bodies are not in evidence. In other respects, the characteristics of a human head are those of that type of human, and are described under human figure.
As with animal’s heads, human heads must be specifically blazoned as couped or erased; couped heads are far more common. While the dexter-facing heads are couped at the neck, children and maidens are sometimes shown as a bust, showing the shoulders (and, in the maiden’s case, the bosom). This is not an ironclad rule, and seems to be artistic license; if the shoulders are meant to be included, they should be blazoned.
One instance exists in Society armory of “heads of St. Cybi”. St. Cybi was a 6th Century Cornish bishop, and is shown as a tonsured monk with a mitre.
The “Janus head” is taken from representations of the Roman god of beginnings and endings. We’ve an example from period Italian heraldry, in the arms of Banda, c.1550 [BSB Cod.Icon 276:15; cf. also Woodward 201].
Also included in this category are the heads of humanoid monsters, particularly those which exist only as a head. Preeminent among these is the “cherub”, or “cherub’s head”: a child’s head cabossed, with two wings. Cherubim are found in the canting arms (Italian angeli, “angels”) of Dianiolli, c.1550 [BSB Cod.Icon 272:277]; Legh, 1576  likewise describes the cherub’s use in armory.
The “seraph”, or “seraph’s head”, is a child’s head cabossed, with six wings; Guillim, 1610  gives an example of its heraldic use (misblazoning it as a “cherub with three pairs of wings”). In the Society, the seraph’s “proper” coloration is with pink skin, red hair, and rainbow-colored wings. The seraph should not be confused with the “standing seraph”, a variant of the angel, which is shown with a full body; as an heraldic charge, the standing seraph appears to be unique to the Society.
The “gorgon’s head”, taken from the monster of Greek myth, is a woman’s head with serpents for hair. As an heraldic charge, it’s shown in Bossewell, 1572 [III.22º]. The gorgon’s head is almost invariably cabossed, but the posture should nonetheless be blazoned explicitly. Finally, there is the “demon’s head”, horned and ugly, much like a Notre Dame gargoyle; this appears to be unique to the Society.
David of Moorland bears: Vert, on a bend Or three Moor’s heads couped sable.
Owain of Holyhead bears: Vert, three heads of St. Cybi proper aureoled Or.
Talanque bears: Azure, a horned demon’s head erased Or.
Petra Malusclavus Africana bears: Per pale azure and gules, a gorgon’s head cabossed argent.
John of Coventry bears: Bendy gules and argent, a Turk’s head affronty couped proper impaled upon a spearhead couped sable.
Staffan Arffuidsson bears: Azure, three seraphs Or.
Sabina de Almería bears: Or, a cross flory, on a chief purpure three Janus heads argent.