(This is an old log re-published as a post.)
Placing Tiles which are bigger than the Map’s tile size. A reference in the Tiled forums.
Summary of the issue is that multi-selecting tiles in while in Isometric projection does not yield a ‘flat’ orthographic placement of the tile, obviously. Ideally, a multi-selected Tile should be presented as a flat screen-space graphic, but the proper procedure, as Bjorn pointed out in the link above is to use a Collection of Images, so as to obviate the need to select multiple tiles to get to a bigger image.
This is fine in respect to the OP’s problem of putting in establishments. But my issues are putting walls, and all sorts of tiles that need to be connected precisely unto other tiles. The problem is how tiles are aligned in the first place. Tiles are anchored at the lower-left point. That means the bigger the tile gets in relation to the map tile size, the further up and right the tile’s registration will be.
On the outer hand, an Image Object aligns itself with the bottom anchor point making it ideal as a positioning entity.
I went ahead and modified TMX Importer V2 to retrieve the tileset id or image used by the Image Object, but Rex has also modified it after requesting it, so either way this is a doable solution.