PImage img = loadImage("bill.jpg");

float x = 0;
float y = 0;
float step = 1.2;

float initPercentage = 0.1;

float w;
float h;

for (float p = initPercentage; y < height; p++) {
  w = img.width;
  h = img.height;
  for (x = -w/2; x < width; x += w/2) {
    image(img, x, y, w, h);
  }
}