The first villagers that you invite to your town (the two you begin with and any that you encounter on islands before the campsite is built) will all have very basic houses and wallpapers/flooring, and the only way to fix the interior is to gift them things but generally there isnt much you can do to fix the look. If someone comes to your island and asks a villager in one of these generic houses to move to their island, will the villager have an upgraded, individualized house on their island or will they retain the same exterior and interior, assuming they have the campsite as well? I'm pretty sure in other games, NL at least, the villager kept the same interior if it was altered in any way but the way houses are developed in NH are a bit different so I wasnt sure, ;w;