When the localisation imageset refreshes for one person it automatically does it for everyone at every page load, this causes a vast amount of spam in the admin log of (Refreshed "en" localisation of imageset), this will be triggered by anonymous users, bots, registered users and administrators. The result of this causes all the topic icons, post reply icons and other localised images to not appear.
The current workaround is to purge the cache, twice. This issue started after upgrading from 3.0.5 to 3.0.6, it appears that not everyone will come across this error but others have reported it on the support forums.
Also, manually refreshing the imageset, template and theme did not resolve the issue.