Since Confluence doesn't provide a way to delete unused attachments, we often go in and delete the unused images after copying and changing a page. Otherwise it causes Confluence indexing problems as the unused attachments build up over time. Deleting them one at a time is very time consuming.
It would be nice to be able to select multiple attachments to delete as follows:
See also the related feature request to delete unused attachments: https://jira.atlassian.com/browse/CONF-16577