It's not possible to clear (or purge) the variation/alias of images.

Steps to reproduce:

1. Prepare eZ Publish 5.4 installation, with eZ Demo and fully updated to 5.4.1.1;
2. Go to frontend siteaccess i.e. http://54ezdemo.com/;
3. Now go to /ezpublish_legacy/var/ezdemo_site/storage/images/getting-started/selected-features/getting-started-with-ez-publish-platform/322-1-eng-GB/
4. See that "Getting-Started-with-eZ-Publish-Platform_campaign.jpg" image alias is there;
5. On command line, run the following command from the installation's root folder:

$ php ezpublish/console ezpublish:legacy:script bin/php/ezcache.php --clear-id=imagealias --purge
Running script 'bin/php/ezcache.php' in eZ Publish legacy context
Purging imagealias: 
Image alias-

6. Output suggests image alias has been deleted, but that's not the case, as "Getting-Started-with-eZ-Publish-Platform_campaign.jpg" is still there.