I would like to have other logo in a header (white) and other in a menu (white), in Joomla it would be easy.

How can I do this?
#gk-logo-css-big {
background-image: url('yourimage_path.jpg')!important;
}
#gk-logo-css.gk-small-logo {
background-image: url('yourimage_menu_path')!important;
}