Style the recommended posts?

At the bottom of every post there's are two simple links to encourage readers to read the next - or previous - blog posts. These are simple blue links - I believe that this is the code:

<span class="cat-links"><span class="gp-icon icon-categories"><svg aria-hidden="true" height="1em" viewbox="0 0 512 512" width="1em" xmlns="http://www.w3.org/2000/svg">
<path d=""></path></svg></span><span class="screen-reader-text">Categories</span> <a href="https://boo.com/category/blog-post/" rel="category tag">Blog Post</a></span>

<nav aria-label="Single Post" class="post-navigation" id="nav-below">
  <span class="screen-reader-text">Post navigation</span>
  <div class="nav-previous">
    <span class="gp-icon icon-arrow-left"><svg aria-hidden="true" height="1em" viewbox="0 0 192 512" width="1em" xmlns="http://www.w3.org/2000/svg">
    <path d="" fill-rule="nonzero"></path></svg></span><span class="prev" title="Previous"><a href="https://boo.com/is-it-worth-it/" rel="prev">This Post</a></span>
  </div>
  <div class="nav-next">
    <span class="gp-icon icon-arrow-right"><svg aria-hidden="true" height="1em" viewbox="0 0 192 512" width="1em" xmlns="http://www.w3.org/2000/svg">
    <path d="" fill-rule="nonzero"></path></svg></span><span class="next" title="Next"><a href="https://boo.com/employment-market/" rel="next">That Post</a></span>
  </div>
</nav>

So, my question is - could we - for example, pull in the thumbnails of those posts to make them more clickable? Is this done via the PHP templating or could an Element work here?

Thanks!