With this latest update, Sony have yet again decided to use their own custom - and much worse - icons for various system apps.
I've uploaded the stock Android Ice Cream Sandwich app icons here: http://db.tt/5CKPzYBo
You can then use the excellent and free app, Desktop VisualizeR, to add custom icon widgets to your home screen to launch apps. There's no way to change the actual app icons in the App Drawer or when in the app itself, but at least you won't have to look at the ugly new ones as often this way.
HTH
Matt
