Usually in games once you’ve chosen your character, you’re more or less stuck with it in terms of certain features, like the character’s face, hair, eyes, nose, and etc. There are some things that can be changed, like armor, but if you wanted to change the way a character looks on a base level (such as expressions), once you’ve made your choice you’re pretty much stuck with it.
That’s the same thing that’s happening with Capcom’s recently released Monster Hunter: World, but the good news is that Capcom could be considering changing that. In a recent interview with GAME Watch (via Siliconera), the game’s producer Ryozo Tsujimoto revealed that if there is enough demand for it, post-creation character customization could be a feature that Capcom will consider in the future.
Tsujimoto was quoted as saying, “You can’t redo it, but when making a character you can check their expressions, so you might want to do that first while making a character. However, if there’s enough demand for it then I’ll put it under consideration.” This seems to follow reports of players who spent quite a lot of time in the character creator, only to find out that the actual facial animations and lighting aren’t as accurate as they had thought.
Note that this is by no means a guarantee that it will come, so if you are planning on starting the game, you might want to spend a little extra time deciding if your character’s look is something you can live with for the foreseeable future.