All icons generated by [@ui.macro }} will use BaseURL to generate the {{<img src=""/> attribute. In case of accessing Bamboo using different URL or in case of Bamboo move to another server and not updated BaseURL all those icons might disappear thus making some Bamboo features unusable (ie Scheduled Backups cron expression editor https://support.atlassian.com/browse/BSP-6402?focusedCommentId=2366316&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-2366316)