function array_search ( arr , str ) {
	for ( var i = 0 ; i < arr.length ; i ++ ) {
		if ( arr[i] == str ) {
			return i;
		}
	}
	return -1;
}

function random ( num ) {
	return Math.floor(Math.random() * num );
}

function showImages () {
	var showimages = new Array();
	var count = 0;
	while ( count < 4 ) {
		var image = image_list[random(image_list.length)];
		if ( array_search ( showimages , image ) == -1 ) {
			showimages.push ( image );
			count ++;
		}
	}

	for ( var i = 0 ; i < showimages.length ; i ++ ) {
		document.getElementById('client'+i).style.background = 'url('+showimages[i]+')';
	}
}