ClickOnce-Apps can have customized icons for the start menu and desktop shortcuts. Sadly, the icon in "Add/Remove" is always the ClickOnce standard icon from the unmanaged ClickOnce API dfshim.dll.
However, the icon can be modified via the Registry. The registry key can be found beneath HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall. So you can set an icon of your own on first run a described on StackOverflow.