Unfortunately, I don't think this is not supported by Install Shield Limited Edition. From the Flexera website product features:
Specify Custom Icon and Version Resource Properties Modify the icon and version resource properties to match your company and product branding.
This only has ticks for the Premier and Professional versions of Install Shield, and I think this is talking about the installer's icon.
This leaves a tool such as Resource Hacker, but as eggy pointed out, this could cause problems.