PImage[] pix;
int frame = 0;

void setup(){
  size(640, 480);
  pix = new PImage[7];
  for(int i = 0; i<7; i++){
    pix[i] = loadImage("Frame "+(i)+".jpg");
  };
}
void draw(){
  image(pix[frame], 0, 0, 640, 480);
};
void mousePressed(){
  frame++;
  frame%=7;
};