function affiche_liste_fond() {

	if (document.getElementById('old_theme').value != '') {
		document.getElementById(document.getElementById('old_theme').value).style.display = 'none';
	}
	document.getElementById('old_theme').value = document.getElementById('theme').value;
	if (document.getElementById('theme').value != '') {
		document.getElementById(document.getElementById('theme').value).style.display = 'block';
	}
}