Terrain tile graphics could "attach" to adjacent tiles

[pender]

Right now we use a different wall tile if the tile immediately beneath it is also a wall tile. We could extend this to use different images based on the four or eight adjacent tiles.

Example of what I'm talking about -- six tilesets in which the tile is selected based on their eight neighbor tiles

And this is the template they're using:

Simpler to use only the four adjacent tiles; then we need only 16 images for each tile and choose them as a binary bitmap of the four adjacent:

I think an approach like this could be a good way to level up the appearance of obstruction and liquid tiles in particular.