randomising images in a table

Hiya

I have a 4x4 table and i have 16 set images to appear in each of the cells. How do i code a function so that the images appear in a randomise fashion when a button on the website is clicked

Array.prototype.swap = function(index1,index2)
{ var temp = this[index1];
this[index1] = this[index2];
this[index2] = temp;
return;
}

Array.prototype.shuffle = function()
{ for(var i=0; i<this.length; i++)
{ ind1 = Math.floor(Math.random()*this.length);
ind2 = Math.floor(Math.random()*this.length);
this.swap(ind1,ind2);
}
return;
}