Multiple images store in variable and render on twig file.

Yes, we have option for render multiple images on any template file. We just have to create variable in .theme file and collect in array and then print array value by variable.

Example: First we have to take the step on hook_preprocess_node(&$variables). we have to check node value is available or not.

if(isset($variables['node'])){

    $node = $variables['node'];

    $current_node_id = $node->id(); //get the current node id

    $node_type = $node->type->target_id;  //get the current node type

    if($node_type == "applications"){  // we are going with example of applications content type nodes..
  
    /*  Now we will get the fields by node::load  */
  

    $categoryid = $node->get('field_category')->target_id; //here field_category is Category field machine_name..

        $category_detail = \Drupal\taxonomy\Entity\Term::load($categoryid);

        $variables['category_name'] = $category_detail->name->value;  // get the category name

        $variables['landing_page']  = $category_detail->field_setup_landing_page->value;  // get the field_setup_landing_page field value     

        /* here 'category_name' and 'landing_page' is our variable keys */    

        $node_detail = Node::load($current_node_id);                          


        $node_id = $node_detail->id();                   // get the node id

        $node_title = $node_detail->getTitle();          // get the node title

        $node_Published = $node_detail->isPublished();   // get the publish status

        $node_type = $node_detail->getType();            // get the node type

        $node_field_model_value = $node_detail->get('field_model')->value;   // get the field model value

        $node_field_price_value = $node_detail->get('field_price')->value;   // geth the field price value

         $img_urls = array();
        foreach ($node_detail->field_image as $item) { // get the field image with multiple image url
          if ($item->entity) {
            $img_urls[] = $item->entity->url();
          }
       
        }


        /* Now put the all values in array with keys for differentiate */

        $arr = array('id'       => $node_id,

                     'title'    => $node_title,

                     'published'=> $node_Published,

                     'type'     => $node_type,

                     'model'    => $node_field_model_value,

                     'price'    => $node_field_price_value,

                     'image'    => $img_urls

        );


        /* Now pass the $arr in final productfields variable like this.. */

        $variables['productfields'] = $arr;  

        This is our final product fields variable now we have to move on applications type twig file because we are working for specially applications type of contents.

        Suppose are applications type twig file name is 'node--applications--full.html.twig'. That file is for applications detail pages.

        <ul>

        {% for key, value in productfields %}
        {% if key == 'image' %}
            <ul>
            {% for keys, imgvalue in value %}
                <li class="{{ keys }}"><img src="{{ imgvalue }}"></li>
            {% endfor %}
            </ul>
        {% endif %}
        {% endfor %}  

        </ul>

  /* here 'productfields' is same variable name which we are created in 'hook_preprocess_node(&$variables)' hook in .theme file, so we just have to print the array keys and value by for loop in Symphony syntax, So that is the easy way to create custom variable and then render values in twig file. */

    }      

}

Note: If have any suggestions or issue regarding 'Multiple images store in variable and render on twig file.' then you can ask by comments.

Create custom variable in drupal 8 and render on template file.

We have alternate option for custom variable in drupal 8. Now we will going to describe that how to create custom variable and use on any template file.
here we are going to giving an example with easy steps for custom variable use and render on file.
Example: First we have to take the step on hook_preprocess_node(&$variables). we have to check node value is available or not.
if(isset($variables['node'])){
    $node = $variables['node'];
    $current_node_id = $node->id(); //get the current node id
    $node_type = $node->type->target_id;  //get the current node type
    if($node_type == "products"){  // we are going with example of products content type nodes..
   
    /*  Now we will get the fields by node::load  */
   
    $categoryid = $node->get('field_category')->target_id; //here field_category is Category field machine_name..
        $category_detail = \Drupal\taxonomy\Entity\Term::load($categoryid);
        $variables['category_name'] = $category_detail->name->value;  // get the category name
        $variables['landing_page']  = $category_detail->field_setup_landing_page->value;  // get the field_setup_landing_page field value
       
        /* here 'category_name' and 'landing_page' is our variable keys */
       
        $node_detail = Node::load($current_node_id);                           

        $node_id = $node_detail->id();                   // get the node id
        $node_title = $node_detail->getTitle();          // get the node title
        $node_Published = $node_detail->isPublished();   // get the publish status
        $node_type = $node_detail->getType();            // get the node type
        $node_field_model_value = $node_detail->get('field_model')->value;   // get the field model value
        $node_field_price_value = $node_detail->get('field_price')->value;   // geth the field price value
        $node_field_image_value = $node_detail->get('field_image')->entity->uri->value; // get the field image with single image url

        /* Now put the all values in array with keys for differentiate */
        $arr = array('id'       => $node_id,
                     'title'    => $node_title,
                     'published'=> $node_Published,
                     'type'     => $node_type,
                     'model'    => $node_field_model_value,
                     'price'    => $node_field_price_value,
                     'image'    => $node_field_image_value
        );

        /* Now pass the $arr in final productfields variable like this.. */
        $variables['productfield'] = $arr;
       
        This is our final product fields variable now we have to move on products type twig file because we are working for specially products type of contents.
        Suppose are products type twig file name is 'node--products--full.html.twig'. That file is for products detail pages.
        <ul>
        {% for key, value in productfield %}
       
        <li>{{ key }} | {{ value }}</li>
       
        {% endfor %}   
        </ul>
       
        /* here 'productfield' is same variable name which we are created in 'hook_preprocess_node(&$variables)' hook in .theme file, so we just have to print the array keys and value by for loop in Symphony syntax, So that is the easy way to create custom variable and then render values in twig file. */
    }
       
}

Note: If have any suggestions or issue regarding 'Custom variable in drupal 8 and render on template file.' then you can ask by comments.