/data/iconsets/iconsetname/size/message.png should be named event.png
This icon is often draw as a message/mail/bubble icon because of it name "message.png", but it's used to warn about messages but also chatrooms invitation, file transfer request, add request... So the name is bad, and drawers (me for example) will stupidly draw message/mail/bubble icon. People actually see this kind of icon for all types of events, and it's not consistent at all.