This scriptlet should let you set a new tileset as the default one for any given map via script call.
The main idea behind it is to replace the default tileset with another one with some tiles changed for any specific reason, like different house facades or withered trees or an open well or all of them at the same time.
It is pretty much like a method to stop making dozens of events to cover those areas. This might be especially useful if the changes are supposed to last for a long period of time or even for the rest of your game.
It DOES refresh the current map and its spriteset.
The script will also work on other maps, obviously.
Warning
If you have implemented other scripts that have changed how the Game_Map class works, make sure you place this script above all of them.