gimp-elsamuko
Film Grain Script
This is a script which simulates the typical film grain of high ISO pictures. It’s a script of this tuorial.
Copy it into the scripts folder from GIMP, you will find it then under Filters → Generic → Film Grain.
Holdness and Value are two options directly taken from HSV-Noise, Strength changes the amount and area of grey, which will turn grainy.
It works together with colored and greyscaled pictures.