Add fill command for particles effects?

Ive been trying to figure out a way to fill a room with a blackish white particle effect to make the upside down from stranger things but I can't seem to get the particles to stay in the location. I'd love you added this because it would help a lot of map creators permanently add particles to an area to make it look more lively. I think it would be done best by just adding to the fill command by adding [particle] [particle type] after you type /fill so you can either fill with blocks or particles. Thanks <3