Please confirm if a change of alarm icon at one site would impact all other sites.
Yes, a change to the alarm type icon are experienced at all sites. Alarm types are global value list objects and the alarm icon is an attribute of that global value list object. This is the same for most of the value lists exposed at the site level such as asset type, indicator type, etc.It's an easy fix, just change the icon on the Alarm type. These are found in the Indicator view > Indicator Settings tab > Alarms > Alarms > Alarm Types page.