The preloader image can be changed from the following image tab which is located at the beginning of each page:

<div id="sh__page-loading" class="sh__pageLoading sh__preloaderBreath">
  <div class="sh__pageLoading-inner">
    <img src="img-assets/logo2.png" alt=""> <!-- Change the preloader image -->
  </div>
 </div> 

If you want to remove the preloader animation you can simply remove the sh__preloaderBreath class from the above code.

The preloader style can be found in app/css/scss/_general.scss > page preloader. Also the preloader function is located in app/js/src/script.js > enablePreloader.