Walls! I went through some iterations, and am unlikely to use these ones with torches. It served its purpose, though, letting me explore things like adding lamps to the walls and lighting.
I also added some scenery to the walls. Rubble piles, picks, shovels and buckets. It turns out everything I've done is way too dark (more on that later...) so I think it looks great and atmospheric on my bright screen, but on paper, it's muddy poo.
I expect to make a cave system too, not just mine tracks and walls with support beams - something more organic. I made some 3" wall pieces that provide for doors, archways and additional supports:
Just another pic of some in progress walls. There are picks in various positions, and shovels and buckets.
These are the lamps I worked out. I might still play with the contrast a bit, but not until I solve other issues.
So, those are the walls. Next post will be the tiles.