Hi,
you wouldn't need more than one Timer for that, because there is nothing happing parallel, it's just a sequence(45, 10, 5).
You just have to know in which state of the sequence you are currently in. When the timer finishes, increment the state-variable and restart the timer with a new totalTime. Something like this:

1. Timer timer;
   PImage[] images = new PImage[2];        // array to store the images
   int[]times = {2000, 3000, 4000, 1500};  // the time how long each image should be displayed
   int state = 0;  
   
   void setup() {
     size(300, 300);
     timer = new Timer(times[0]); 
     images[0] = loadImage("image.jpg");
     images[1] = loadImage("painting.png");
   }
   
   void draw() {
     background(0);
     // show image from images-array(begin with first agin, if there are more states than images)
     image(images[state%images.length], 0, 0, width, height);
   
     if (timer.isFinished()) {
       // increase state (begin with 0 again, if state is higher than the size of 'times")
       state = (state+1)%times.length;
      
       // restart timer with new totalTime
       timer.totalTime = times[state];
       timer.start();
     }
   }
   

Cheers for the reply