umm...no...thats how you theme an app, not the system. opening up and editing random apks is not what is ment by themeing. that just moddifies that app and that app only! a true theme (i.e. notification bar and system png's) is done with either metamorph or by manually editing the framework-res.apk, then if you want to take it further you edit the dialer and app drawer and that is a theme. modding other apps just adds continuity throughout the theme, but you need the basics first.
@2FR35H for true "themeing" you can find the apks you need listed below!
Notification Bar and system images:
/system/framework/framework-res.apk
dialer:
/system/app/contacts.apk or TouchWizContacts.apk (depending on what rom you use)
app drawer:
/system/app/Launcher.apk or TwLauncher.apk or AdvancedLauncher.apk or others (depending on what launcher you use and want skinned)