InstantCommons does not work on Vagrant if you enable the 404 handler for images (the thumb_on_404 role does that and most multimedia roles include it). The problem is related to thumbnail caching; similar to T101565, but the default wiki (127.0.0.1) is also affected.
As a workaround, caching can be disabled by creating /vagrant/settings.d/10-DisableThumbnailCaching.php with
<?php $wgUseInstantCommons = false; $wgForeignFileRepos[] = array( 'class' => 'ForeignAPIRepo', 'name' => 'wikimediacommons', 'apibase' => 'http://commons.wikimedia.org/w/api.php', 'fetchDescription' => true, 'descriptionCacheExpiry' => 0, 'apiThumbCacheExpiry' => 0, );