View mode template for user-profile.tpl.php? I can set up a view mode for the user profile, but I don't know how to create a template targeting it. user-profile.tpl.php is the template used, but I can't figure out how to make a view-mode targeted version of it.

Any suggestion?
You already figured out how to create an additional view mode for the user entity:

/**
 * Implements hook entity info alter
 * Adds additional view mode for user entity
 */
function MYCUSTOMMODULE_entity_info_alter(&amp;$entity_info) {
  $entity_info['user']['view modes']['teaser'] = array(
      'label' =&gt; t('Teaser'),
      'custom settings' =&gt; TRUE,
  );
}


Now you can define theme suggestions for that view mode using HOOK_preprocess_user_profile:

/**
* Implements HOOK_preprocess_user_profile()
* Adds theme suggestions for the user view mode teaser
*/
function MYCUSTOMMODULE_preprocess_user_profile(&amp;$vars) {
  if ($vars['elements']['#view_mode'] == 'teaser') {
    $vars['theme_hook_suggestions'][] = 'user_profile__teaser';
  }


After clearing the caches Drupal will search in the theme folder for a file called user-profile--teaser.tpl.php, which could look like this example*:

&lt;section class="user-teaser"&gt;
  &lt;?php print render($user_profile['field_last_name'][0]); ?&gt;
  &lt;div class="user-image"&gt;
    &lt;figure&gt;&lt;?php print render($user_profile['field_user_picture'][0]); ?&gt;&lt;/figure&gt;
  &lt;/div&gt;
  &lt;div class="user-body"&gt;
    &lt;?php print render($user_profile['field_biography']); ?&gt;
    &lt;?php print render($user_profile['field_birthdate']); ?&gt;
    &lt;?php print render($user_profile['field_nationality']); ?&gt;
  &lt;/div&gt;
&lt;/section&gt;


(* actual code will depend on the fields you defined for the user profile)