トップページに背景画像を表示したい

<%= render "shared/header" %>
<div class="main_contents">
  <div class="post_contents">
    <h2 class="title">新規投稿</h2>
    <ul class="post_lists">
      <% @posts.each do |post| %>
        <li class="list">
          <%= link_to post_path(post.id) do %>
          <div class="post_img_content">
            <%= image_tag post.images[0], class: "post_img" if post.images.attached? %>
          </div>
          <div class="post_info">
            <h3 class="post_date">
              <%= post.date %>
            </h3>
            <h3 class="post_title">
              <%= post.title %>
            </h3>
          </div>
          <% end %>
        </li>
      <% end %>
    </ul>
  </div>
</div>

/* 投稿内容表示ページ */
.main_contents {
  background-image: url("/images/top_view.jpg");
}

.post_contents {
  background-color: rgb(248, 227, 247);
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 10vh 0;
}

.post_contents>.title {
  font-size: 5vh;
  line-height: 1.4;
  font-weight: bold;
}

.post_lists {
  width: 100vw;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;  
}

.post_lists>.list {
  width: 37vh;
  padding: 1vw;
  background-color: rgb(248, 227, 247);
}

.post_img_content {
  position: relative;
}

.post_img {
  width: 33vh;
  height: 33vh;
}

.post_info {
  background: rgb(248, 227, 247);
  color: black;
  padding: 1vw;
}

.post_date {
  font-size: 2.5vh;
}

.post_title {
  font-size: 2.5vh;
}

/* 投稿内容表示ページ */