I made this, just as a proof of concept that 3D walls are fully possible witth the new system. Also it's up to you to decide wether filling in the black with a texture is a good thiing or not.
I just have to say, I love the colors a LOT. It reminds me of old games with colorful pixelart, and really livens up the picture. The colorfulness, and the contrast between dark and light colors, is key! But alas, it overshines everything else from the spritesheet. I Think for this to match up, the colors need to be more saturated, even tho that is a shame, and i would love for the colors in the steam spritesheet to be revisited, for less saturation, tho that would be a Lot more work.
Maybe the shadows could be made more dark Blue Than grey, just as an example (for the steam sprites) to just deepen the colours, and create that real depth and colorfulness there is in Everything.
I Know its a Weird exapmle, but manhunt (the sick rockstar game) has a generally very, very vibrant colorpalette, Even though the setting is Very dark and "grey", with concrete walls everywhere, and the places are general not very bright. But, The colors theyve used, makes it so Beautiful. Even a brick wall is beautiful in that game. And all the textures are like that, vibrating with color, shadows containing different shades of purple, red and blue, Even tho the object itself couldve just been made grey, like a rock, but they choose to go with colors. Black doesnt Really create darkness, more than some colors do. And colors are Beautiful and memmorable, Where high saturation makes Nothing really stand out. I know its the point for some things, to not make a chaotic mess of colours, but i think it would be Beautiful with a bit more color. It makes it more of a "painting", in a sense.
Another good examples is Heroes of might and magic III, where the fog of war, consists of beautiful shades of dark blue, almost black looking. Everything is vibrating with color. Light is anything but white, and darkness is anything but black, (except for darkness with a complete lack of light ofcourse, like at the bottom of the ocean).
But in general, i Think using too much black, and shades of grey, Should be avoided.
I would love to See you make a tileset with colors like this, after the graphics coding has been done.
I do also think, that what is unexplored, should stay black, or some other fog of war texture (homm3?).
The exposed walls could have your textures (since youve revealed the material type) and fade out into the unexplored tiles with fog of war. I would really love that. And i like the way youve done it, with the fading material types.
Also, the walls "rock border" sprite, i dont think it Should be there, when the solid material meets Another solid block, like a ramp (like in the top right of the image). It Should only have the rock border, when the wall is exposed, to simulate support made of stacked rocks, if it is Indeed a soil layer. Hope you understand my wording.