[Balanor]

Yes, copying one of the existing Building areas and then modifying that copy is probably the easiest way to start. However, if you want to use a different tileset, then make sure you look at the Properties of one of the existing areas and put the 3 scripts in the area events. It's a little more manual work to do that, which is why I just setup the how-to document to make a copy of an existing area.

You can change the appearance of the interior door, yes. In fact, I'd encourage it.

You can create your own custom sounds as well. BUT, the sounds really need to match what is in the tile without too much embellishment. This is because, as you alluded to, that a floorplan you create could potentially be used by others as well. So rather specific sounds, like prostitute calls in an area you are planning to make a brothel (for example), I will likely end up taking out since not everyone may use that floorplan/room for a brothel. In your example, if you actually place a smithy room from the tileset, then smithy sounds in it are very appropriate no matter who has that floorplan.