[zebra]

Вы уверены?

function myImages(){
    var self = this;
    this.images = new Array();

    this.add_img = function(count){
        self.images.push(count);
    }
}
var o = new myImages();
o.add_img(1);
alert(o.images);
o.add_img(2);
alert(o.images);