Below is the code I used to make this,

Thanks!(:

PImage img1, img2, img3, img4;

void setup(){
size(990, 1250);

img1 = loadImage(“fstein_top.png”);
img2 = loadImage(“fstein_bottom.png”);
img3 = loadImage(“monster_top.png”);
img4 = loadImage(“monster_bottom.png”);
}

void draw() {

image (img1, 0 ,0);
image (img2, 0 ,height/2);

if(mousePressed && mouseY<height/2) {
image(img3, 0, 0);
}

if (mousePressed && mouseY>height/2) {
image(img4, 0, height/2);
}

}