Are there any black people in Scadrial? Or any other races? I couldn't find an answer online, but the descriptions in the book all seem like white/European people.
The Terris had a lot more skin color diversity than the people of the central dominance. A large number of those preserved had darker skin, so in the W&W era, you are starting to see skin color become associated with them. During the Final Empire, skin color was basically ignored.
Note that for even people in the Elendel Basin, darker skin won't get nearly as dark as what you will find on Roshar or Taldain.
EDIT: Now that I'm on my computer instead of my tablet, I can dig into this a little more. What other posters have been saying is true--the region of the Final Empire we see in the first trilogy is very small, and the Final Empire itself isn't terribly big. There's not a lot of racial diversity at all.
That said, the Terris are a distinct ethnic group. I carefully didn't describe people in the original books with regard to a lot of racially identifying features. One of the Lord Ruler's goals over the years was to stamp these things out, to create a single unified people. While he couldn't change genetics, his work here did make people start to look at things like class and clothing more than accents or racial identifiers. In addition, it was important that the Terris be diverse enough that, while some looked Terris from just a glance, with others, you could meet them and (for obvious reasons that are spoilers) not know they were actually Terris.
That isn't to say they aren't there--they actually are. Elend and Straff would have a bit of an accent, and Cett a fairly strong one. Sazed would look racially distinct from Vin.
As we get further from the Final Empire, we see these things becoming more of a marker. The Terris work to preserve their cultural heritage, and this distinctiveness highlights other aspects about them, including the dark skin that many of them brought through the end of the world. The next trilogy (1980's era) is planned to star a Terriswoman right now, and she would likely resemble someone ethnically black to many of us on Earth.
How far off your impression of Sazed was I in imagining him looking like Teferi from MTG?
I often give him a Teferi-like-look in my own head, but in actuality his skin tone is probably more akin to someone like Keegan-Michael Key.
>While he couldn't change genetics, his work here did make people start to look at things like class and clothing more than accents or racial identifiers.
How did the 'skaa/noble' class genetic tinkering work out, anyway? Did the leadership of every nation just wake up the next morning and find themselves taller, more intelligent, and less fertile?
Most genetic differences between skaa and noble were exaggerated, even fabricated, by noble culture as justification for their perceived superiority. Height differences due to nutrition, 'intelligence' due to education and societal expectations, fertility due to common factors in urbanization. The LR did try some minor tinkering, to be played out over time through genetics, but in the end these changes weren't very successful.
This is actually good to know. I've seen your other responses to similar questions, where the inference was that there was indeed a significant difference.
The main changes were for dealing with the atmosphere, correct? And they were reverted by Sazed/Harmony?
There were also some general hardiness changes for the skaa and some fertility changes, but as I said, by the time of the books those were basically gone. And yes, Sazed reverted the ones designed to help survival in the ash.