yield OnGUI

Create new function which does the yields, after each do simple manipulations with booleans.

 // create boolean for each image, like in this example each "showimage" is a bool.
 function WaitFuntion(){
 showimage1 = true;
 yield.....
 showimage1 = false;
 showimage2 =true;
 yield.....
 showimage2 = false;
 showimage3 = true;
 //etc
 }
 
 //And in gui function create simple if statements
 
 function OnGUI(){
 
 if(showimage1 ==true) {//image 1 gui rect }
 if(showimage2 ==true) {//image 2 gui rect }
 if(showimage2 ==true) {//image 3 gui rect }
 
 }

//Remember to set everything on false in the start function