var arrCountries = new Array(6);
var rg = 5; 
var rs = 1 + Math.floor(Math.random()*rg); 
if (rs >= 5) {
rs = 5;
}
arrCountries[1] = '<img src="images/image1.jpg"></img>';
arrCountries[2] = '<img src="images/image2.jpg"></img>';
arrCountries[3] = '<img src="images/image3.jpg"></img>';
arrCountries[4] = '<img src="images/image4.jpg"></img>';
arrCountries[5] = '<img src="images/image5.jpg"></img>';
cdn = arrCountries[rs];
document.write (cdn);