You can display an iPad optimized icon for users who run your non-Universal iPhone app on their iPads.
While Xcode 4 may not give you the option of adding an iPad icon in the Summary tab, you can follow Apple’s documentation to add an icon for iPad users even though the app is not made for iPad.
Rename it to Icon-72.png.
Add it to your project.
You can also do the same for search results icons. This way, iPad users that want to use your iPhone binary app can have a crisp, sharp looking icon on their homescreens.