During advertisement, the installer installs all the icons listed in the Icon table on the user's computer. Having unused icons in the Icon table does not prevent the installation from running, however it does unnecessarily increase the size of the .msi file and the time and space required to advertise a feature.
If an icon is not referenced in the property or table and there is no UI provided to create a reference at run time, you should remove the icon to achieve better performance.
ICE36 reports the following error for the example shown.
Icon Bloat. Icon Icon4 is not used in the Class, Shortcut, or ProgID table. This adversely affects performance.
Icon Table (partial)
ProgID Table (partial)
Class Table (partial)
Shortcut Table (partial)