You need to change the icon by pointing to the file representing the icon they would like to use (e.g. adobe.ico or generic.ico). The icons that are shipped with ITMS are stored as files somewhere on the SMP Server (Notification Server). Where are those located?
ITMS 8.5 and later
Location of default Software icons on the SMP server:
<install drive>:\Program Files\Altiris\SoftwareManagement\Web\Images
When you click on the "Change Icon", it goes directly to the previously used location (in case the customer used their own custom icons) and not to the location where the default icon is. By default, the first time that "Change Icon" is clicked, it will take the User to the default location mentioned above.