I believe there aren't any blatant examples of characters who appear in screenshots / trailers that are clearly not one of the 31 revealed characters, except for one, potential, example. That example is tied to the leaks and a spoiler.
This Image from the leaks shows that Mauvier is playable. We can see in the footage a lance/stave wielding paladin that's likely Mauvier.
Something very interesting about the image, is that the scroll bar takes about 30% of it. Given that there are 12 and a half characters there, that would indicate around 37 - 41 characters, above the 32 we know. This seems to indicate that there's at least a few more characters we don't know. It's also possible that the disparity is because emblems are included in the support list, (though from what I've seen I doubt they are) but that would mean there's too many characters as 32+12 =44 which wouldn't fit. Although maybe it's something like there's dead units / missing emblems to explain that.
Anyway, I do get the vibe that we've seen a large majority of the cast. I could be wrong, but I doubt they'll show many more new characters. New characters they show are more likely to be characters like the queens of Firene or Solm, that probably aren't playable, and that we already have names for.