There is no one concept idea for black or grey tattoos. You can get anything you want tattooed on your body. The most common tattoos in the monochromatic color schemes (black, white, grey) are words, mostly written in old English fonts. Art or pictures that are supposed to look creepy or scary are usually inked in black and grey. I guess it makes sense since it coinheres with the same concept of dark coloring. Black and grey tattoos are the classic colors or non colors of tattoos. You really can’t go wrong with it.