Workman-Dead.icns is from http://www.iconarchive.com/show/halloween-avatars-icons-by-deleket/Red-Skull-icon.html

License:

Artist: Deleket (http://www.deleket.com/) (Available for custom work)
License: CC Attribution-Noncommercial-No Derivate 3.0
Commercial usage: Allowed (Author Approval required -> Visit artist website for details).