I've just bought the portrait pack, so here are my first-hand impressions. While some portraits are admittedly quite nice, OrdepNM's above observations are quite accurate. In short, the skin tone is absurd. Also, almost everybody has a tendency towards chubbiness. Many of the portraits are just not adequate for the Mediterranean populaces they are supposed to represent. Southern nobility look like they're working fields in Mesopotamia all day or something along those lines. Some of them barely have an indo-european feel at all. The "weird cartoonishness" is also true and similar to the Russian pack.
I'm ticking it off in the launcher because they change the looks of my king's ancestors that I've been used to looking different. But I'm not sure I will actually put it back on. To tell you what, those guys the way they looked when I actually played them, had the feel of a sleek Italian chico or a noble Roman lady. But when I launched the game with the new portrait pack, well... it just couldn't stand. I hand to relaunch the game without the pack.
For the record, both Italians and even northern Europeans can be as dark as those portraits. But not basically every single one of them. A street in Rome is different from a village in Turkish Kurdistan. And I've been to both.