Shadestone

Minecraft definitely needs more smokey-blue stone blocks. Deepslate and basalt are as close as it gets to this colour.
However, a new smokey-blue stone block would be such a good looking block for a gloomy setting! Perhaps it could be called shadestone and crafted by combining stone or cobblestone with soulsand/soil. It could then be smelted and crafted into bricks. Chiseled shadestone bricks could have the carving of a soul in the centre (similarly to how chiseled netherbrick has a carving of a Wither) for that ghostly aesthetic. I think this is a marvellous idea, since it is simple and it does not stray far from the vanilla feel of Minecraft!