Formating option fixture

Example:
images: {
type: Types.LocalFiles,
dest: './public/assets',
format:function(file){
	return 'img src="/assets/'+file.filename+'?dim=160x160"&gt;'
}
}
Wouldn't it return the previous value if there is no formatter? Why has the default changed to `path.join(this.href(item),'?dim=160x160')`?