function(theme) {  
            var preview     = this.preview;
            var oldTheme    = this.settings.previewTheme;
            var themePrefix = this.classPrefix + "preview-theme-";
            
            preview.removeClass(themePrefix + oldTheme).addClass(themePrefix + theme);
            
            this.settings.previewTheme = theme;
            
            return this;
        }