butter-kanglam-ui/_includes/header.html

<header class="header" style="background-image: url('{{ site.baseurl }}/assets/images/btr-texture.png');"> <!-- set bg url here so we can apply site.baseurl -->
  <div class="container">
    <div class="header-area-wrapper">
      <div class="header-menu">
        <ul class="header-menu-list ls-40">
        {% for lang in site.languages %}
          {% if forloop.index0 == 0 %}
            <li><a href="{{ page.url | relative_url }}" class="darklink">{{ site.data.home.language_selector[lang] }}</a></li>
          {% else %}
            <li><a href="{{ lang + page.url | relative_url }}" class="darklink">{{ site.data.home.language_selector[lang] }}</a></li>
          {% endif %}
        {% endfor %}
        </ul>
      </div>
    </div>
  </div>
  <div class="header-content">
    <img src="{{ site.baseurl }}/assets/images/paddy.svg" alt="Paddy, the Butter Box Mascot" class="header-image" />
    <div class="header-title">{% t butter_box_title %}</div>
  </div>
</header>