A possible way is to draw the image on each draw() loop, and loop a given number of times (can be random between bounds), computing random x and y values (between 0 and width for the first, 0 and height for the second) and drawing a white (or gray with random level) pixel at this position.

i played around with the idea of adding noise to an image a bit.
and got some results that are not that bad.

take a look at this.
you can change the amount of change, with the X and Y mouse Position.

1. PImage img;
   
   
   void setup() {
     img = loadImage("tv.jpg");
     size(img.width,img.height);
     smooth();
     background(255);
   
   }
   
   void draw() {
     background(255);
     image(img,0,0);
   
   
     loadPixels();
     int n = mouseX; // noise volume
    
     for (int i = 0; i < img.pixels.length; i++) {
   
       if(i%int(random(1,mouseY/10))==0){   //only add noise to every X line
   
         pixels[i]  =
           color(
         red(img.pixels[i])+(int)random(-n,n),
         green(img.pixels[i])+(int)random(-n,n),
         blue(img.pixels[i])+(int)random(-n,n)
           ) ;
   
       }
     }
     updatePixels();
   
   }
   
   
   
   
   

btw, i used this image , worked well.

http://www.imuslimz.com/images/tv-channels/GeoTv.jpg