SCREENSHOT SURVIVAL 20XX

The big issue is that realistically the border between two rooms isn't a tile thick (1 tile is approx 1 metre squared) which makes the thickness of the walls (dictated by the ceiling tile) really awkward when it comes to not only areas behind the walls, but also the lead-in area between rooms. General rule of thumb is to use the thickness of the walls for lead-in like I used in the last shot, though you can also move the stone tiles down one more tile and it'd technically work, too - creating a hard-and-fast cut-off between the rooms.

The only real way to get it looking good would be to have B-E ceiling tiles that are about 4-8 pixels wide, but you'd have to have every iteration of the tiles that you'd need when mapping and you run into the issue of tileset space limitation and layer issues. You could alternatively use an image of ceiling tiles over the top, which could work well, actually, but it'd be a lot more work.

(This is the reason that, when using wood floors that I know will be cut off due to changes in the tiles, I use the grain that runs the same way as the 'cut'. So in this case I would have used the wood flooring that runs left-right so that there's none of that awkward half-wood cutoff like in the edited image.)