function img(){
	$('imgEmpresas').src = "images-clientes/" + imagenes[parseInt(Math.random()*imagenes.length-1 )];
}

function traerImg() {
	var request = new Request.JSON({
		'url'		:	'ajax-clientes-chico.php',
		'data'		:	'nc=' + Math.random(),
		'method'	:	'post',
		'onSuccess'	:	function(json) {
			imagenes = json;
			setInterval("img()", 2000);
		}
	});
	
	request.send();
}
traerImg();