         
         // Off Image
         if offImage == nil {
-            let imageStr = NSBundle(forClass: DZCheckBox.self).pathForResource("SwitchBackground_off", ofType: "png");
+            let imageStr = NSBundle(forClass: DZCheckBox.self).pathForResource(defaultOffImageName, ofType: defaultImageType);
             self.offImageView.image = UIImage(data: NSData(contentsOfURL: NSURL(fileURLWithPath: imageStr!))!);
         }
         else {

        
        // On Image
        if onImage == nil {
            let imageStr = NSBundle(forClass: DZCheckBox.self).pathForResource("SwitchBackground_on", ofType: "png");
            self.onImageView.image = UIImage(data: NSData(contentsOfURL: NSURL(fileURLWithPath: imageStr!))!);
            
        }

        
        // Thumb Image
        if thumbImage == nil {
            let imageStr = NSBundle(forClass: DZCheckBox.self).pathForResource(defaultThumbImageName, ofType: defaultImageType);
            self.thumbImageView.image = UIImage(data: NSData(contentsOfURL: NSURL(fileURLWithPath: imageStr!))!);
        }
        else {
