var Array1 = new CreateArray('metro1.jpg', 'metro2.jpg'); 

function CreateArray(){
    this.length = CreateArray.arguments.length
    for (var i = 0; i < this.length; i++)
    this[i + 1] = CreateArray.arguments[i]
}  
 
function randNum (num) {
    var rnd1 = Math.round( (num-1) * Math.random() + 1 )
    return rnd1;
}