diff -u b/src/Plugin/diff/Field/ImageFieldBuilder.php b/src/Plugin/diff/Field/ImageFieldBuilder.php
--- b/src/Plugin/diff/Field/ImageFieldBuilder.php
+++ b/src/Plugin/diff/Field/ImageFieldBuilder.php
@@ -60,16 +60,17 @@
 
         if ($this->configuration['compare_alt_field']) {
           if (isset($values['target_id'])) {
-            $image = $fileManager->load($values['target_id']);
-            $image_style[$field_key]['#thumbnail'] = array(
-              '#theme' => 'image_style',
-              '#uri' => $image->getFileUri(),
-              '#width' => 300,
-              '#height' => 300,
-              '#style_name' => 'thumbnail',
-              '#alt' => 'alt',
-            );
-            $result = array_merge($result, $image_style);
+            $storage = $this->entityTypeManager->getStorage('entity_form_display');
+            $display = $storage->load($field_items->getFieldDefinition()->getTargetEntityTypeId() . '.' . $field_items->getEntity()->bundle() . '.default');
+            if ($image_field = $display->getComponent($field_item->getFieldDefinition()->getName())) {
+              $image = $fileManager->load($values['target_id']);
+              $image_style[$field_key]['#thumbnail'] = array(
+                '#theme' => 'image_style',
+                '#uri' => $image->getFileUri(),
+                '#style_name' => $image_field['settings']['preview_image_style'],
+              );
+              $result = array_merge($result, $image_style);
+            }
           }
         }
       }