I do not know if this also happens when you do not chose for the option to have the cast bar below your character picture.
Whenever i pick a herb, a tiny herbalism icon appears left of the cast bar. When i do other stuff that is related to skills or professions also an appropriate icon appears.
But when i for instance loot a milk barrel along the shore an icon appears that is the face of a person.
Yes, sorry, my bad. This option was not present in vanilla client, I think that this icon really should not be there (or they should configure proper icon for every vanilla cast). The whole reason of this Sam icon is for developers and internal testers to notice the absence of the proper icon and fix it. Player should never see that icon.