Just running the application does not have any effect on the icons of any file types. You would have to explicitly associate the affected file types from within the application or via Windows Explorer to change the icons.
Windows Explorer may do this if you for example double-click an .ico file and then select an application to use to open it. If you did that, you can either manually fix the registry or you can re-associate .ico files with the editor from main menu Tools->File associations... That will set up the previews correctly unlike the Windows Explorer itself.