This one works with keypressed states

basic sketch with states.pde

/* A sketch that has states 
Steve Lambert October 27, 2015
v.01

Note: Add your own images

*/

int state;

PImage acapulco;
PImage acapulco2;
PImage tape;

void setup(){
  size(720,500);
  acapulco = loadImage("acapulco.png"); // Load the image into the program
  acapulco2 = loadImage("acapulco2.png");
  tape = loadImage("tape.png");
  state = 0;
} // end setup


void draw(){

  if (mouseX > width/3){
    state = 1;
  }
  
  
  if (state == 1){
     image(acapulco, 0 , 0, 720, 480);
  }
  
  if (state == 2){
    image(acapulco2, 0 , 0, 720, 480); 
  }
  
  if (state == 3){
      image(tape, 0 , 0, 720, 480);
  }
  
  
} // end draw

void keyReleased() {
  if (key == '1'){
  state = 1;
  } 
  if (key == '2'){ 
  state = 2;
  }
  if (key == '3'){
  state = 3;
  } 

}