[felgall]

Shuffle the arrat and then grab as many as you need off the front.

Array.prototype.shuffle = function() {
   var s = [];
   while (this.length) s.push(this.splice(Math.random() * this.length, 1)[0]);
   while (s.length) this.push(s.pop());
   return this;
}; 

function random_imglink(){
  var myimages = []
    myimages[1] = "01.jpg"
    myimages[2] = "02.jpg"
    myimages[3] = "03.jpg"
    myimages[4] = "04.jpg"
    myimages[5] = "05.jpg"
    ...
    myimages[31] = "31.jpg"

myimages.shuffle();
   
    var rq = myimages[0];
    var rr = myimages[1];
// ... etc