Skull and Face shapes. Variations?

Head proportions are based on many factors, such as brain size, jaw size, vertebral size, vertebral column size, etc. All of these characteristics are defined by different genes/alleles, whether you are a human or some other primate. Between different races, these features vary only slightly relative to the comparison of one species of primate to another (see illustration below).



Are you specifically asking about different face shapes and what genes dictate the type of face shape you've inherited?

I just would love to find an app that lets me change all face/head dimensions of a model within the range that is human. I'd like to see how extreme we can look.

Have you ever used snapchat? It usually sports filters that do things like that. There's also FaceApp

Are they scientific? Using 3D models with names representing every distance variable that we know about?

They're not scientific, but some do a decent job at manipulating facial features. Most end users that use those apps (teens mostly and older people) don't care about those scientific metrics -- in fact, most would find those features a turn-off lol However, I'm certain the designers and coders did their research prior to their implementation. If you're looking for something more comprehensive, you definitely won't find it on an app. I'm not sure who'd be an expert in this sort of thing, as I've never encountered someone in real-life that examines facial morphology for a living (maybe an anthropologist?)