How this cleft is presented in a face portrait can determine a strong aspect of how we interpret character. If it is shallow and elongated it can tend to present a look of severity; if it is deep and relatively short-length, it can deliver a look of sensuousness. Think how the Northern European antique fashion for a beard without a moustache makes the person look rigid and inflexible, it tends to over-accentuate the lower lip and chin making them seem to stick out in a kind of look of stubborn-ness. In a sideways-on silhouette portrait the curve of the Philtrum is especially illustrative of character-type, the straighter its line appears to be the more seemingly severe the character.
Then there are considerations around how the facial aspect is being presented - are we seeing the face from a position above or below? ....which will regulate how much shadow is to be seen in this area. The shadow is important, it is one of the guides to guessing how prominent a projection is the bottom of the nose and how far its tip extends outwards. The shadows are telling us the respective volume and dimensions of each feature relative to the other features.
In presenting an interpretation of the Face of Christ I think that an appropriate expectation is that we are viewing from very slightly below; we are looking up to the image. This means that there will be light shadow playing at the base of the Philtrum and darker, deeper shadow under the base of the nose, but not as much shadow as would be shown were the viewer to be looking down from above. In the various images presented here, one constant has been to present quite a long space between the Upper Lip and the Nose and to throw it into shadow. This then delivers a sense of a man who has a serious nature, a Christ who is a Ruler and a Judge, a person capable of thoughtful consideration and capable of deciding what is right and what is wrong.
I think that an attentive focus upon this relatively very small area of facial landscape can help significantly toward bringing forth a sense of Christ the King.