Agregar textos e imaxes desde CSS

<!DOCTYPE html>
<html lang="es">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .container{
            color:blue;
            padding: 50px;
        }
        .logo:after{
            content:url(./img/logo-agency.png);                      
        }        
        .logo{
            margin:20px auto;
        }
        .container:after{
            content:"String en un div";  
        }
        .imaxedefondo{
            width:300px;
            height:200px;
            background-image:url('./img/header.jpg');
            background-repeat: no-repeat;
            background-position: bottom;
            background-size: cover;
            overflow: hidden;
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="logo"></div>
    </div>
    <div class="imaxedefondo">
    </div>
</body>
</html>