pages/maintenance.twig

<html>
<head>
  <title>{{ store.name }}</title>
  <link href='//fonts.googleapis.com/css?family=Lato:100' rel='stylesheet' type='text/css'>
  <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css"  rel="stylesheet" media="screen">
  <style>
    body {
      margin: 0;
      padding: 0;
      width: 100%;
      height: 100%;
      display: table;
      font-family: 'Lato';
    }

    .container-m {
      text-align: center;
      display: table-cell;
      vertical-align: middle;
    }

    .content-m {
      text-align: center;
      display: inline-block;
    }

    .title {
      font-size: 62px;
      margin-bottom: 40px;
      color: #B0BEC5;
    }

    .store {
      font-weight: bold;
    }
  </style>
</head>
<body>
  <div class="container-m">
    <div class="content-m">
      <h1 class="store">{{ store.name }}</h1>
      <div class="title">Estamos en mantenimiento</div>
    </div>
  </div>
</body>
</html>