I'm not sure why the middle face is shorter in the vertical dimension than the other two -- this probably has more of a technical explanation involving how the pictures were taken or the images recopied than a physical anthropological explanation. I wouldn't be too excited about comparing the composites versus each other since that's so dependent upon how pictures from around the world were taken.
Instead, what I think is interesting is how much each composite is fairly recognizably traceable to relatively close to its country of origin. For example, while looking at one of the composites above, the name "Marianne" suddenly sprung into my mind:
It would be an interesting experiment to do on a large number of people to see how much more accurate their national identifications are when using the 41 averaged composite faces. But also test how well people do on identifying the nationalities of 41 individual faces from the underlying samples.
The existence of types is quite unpopular in the human sciences these days. For example, the Field Museum has a stupendous collection of 104 sculptures they commissioned from sculptress Malvina Hoffman in 1930 to illustrate "The Races of Mankind." In 1999s, I asked a Field Museum official why the museum didn't treat this amazing resource with more respect. She said they weren't realistic because they were "types."
In other words, when Hoffman sculpted, for example, her Nuer tribesman of the Southern Sudan, she sculpted an extremely Nuery-looking fellow imaginable -- about 6'8" and 140 pounds. In reality, by no means is the average Nuer 6'-8". On the other hand, the Nuers, like their archrivals, the Dinkas, are among the most "elongated" people on Earth, so Hoffman definitely caught their particular tendency.
On the other hand, these newfangled composites validate the existence of types.
This is actually an important question to understand both sides of.
Taxonomists rely upon types -- typically a single stuffed animal or preserved plant (known as a holotype) in a prominent museum -- to classify creatures they find. (Any experts in this rather arcane subject, please feel free to correct me.)
For example, say you are a local homeowner and don't like your neighbor's plan to subdivide his land because it would hurt your view and lower your property value. So, you hire some biology grad students to search your neighbor's property for anything that might get him in trouble under the Endangered Species Act. They bring back a dead bird. Is it the officially endangered California gnatcatcher?!? Or is it merely the common Baja gnatcatcher? Huge amounts of money could be riding on this question. You compare it to the type for each and decide based on which it's closest to in looks.
That, however, raises the question of what type of type should be chosen: an average member of a population or a distinctively representative example of a population. Taxonomists have tended toward the latter as being more useful in settling subsequent classification quandaries. For example, a statue of a 6'8" Nuer would be more helpful than a statue of a 6'1" Nuer at helping people subsequently recognize Nuerness.
Somewhat similarly, Swedes tend to be more distinctly representative than, say, Slovenians of certain distinctive tendencies that distinguish Europeans from the rest of the human population. On the other hand, Slovenian are more likely to look like the average European than Swedes do, in part because Slovenia is more central and Sweden more peripheral in Europe.
Do you see the distinction?
Which way of thinking is right and which wrong?
Well, both ways can be useful. It's helpful to be able to remember that there are two different approaches. It's also useful to remember, however, the shortcomings of either approach.
In general, I'm not that big of a fan of the classical taxonomical approach to human beings. Instead, I prefer to think genealogically. For example, instead of trying to match, say, Tiger Woods to his closest type, you just ask him what his family tree is.
P.S. Here's Dienekes's composites of 2006 World Cup soccer players, showing that if you average enough healthy young people together, even Wayne Rooney's team comes out looking all right.