While The Legend of Zelda: Tears of the Kingdom does a lot to differentiate itself from its predecessor, there are some reused assets and concepts from Breath of the Wild. An example of this is in the game's NPCs.
Around Hyrule, you may notice that the people walking its roads and inhabiting its settlements are a little similar to Miis. The modder HEYimHeroic on Twitter has revealed that just like in Breath of the Wild, Tears of the Kingdom uses a modded version of Miis to create NPCs.
By modding the game, you can even import Miis into the world and they'll change based on Tears of the Kingdom's art style. Check out some of the Miis made by HEYimHeroic below: