You should go to the new skinS and theme launches on modmyi.com. They have a separate thread for iPhone 4 only themes. That will definitely wet your whistle. You really should jailbreak. I was apprehensive at first, but it just opens up a whole new world in regards to your phoneAll these cool themes make me want to JB my iPhone. Amazed at all of your creativity.
There is an update slave theme and another slave them called nine hd z. should be on cydia soon. I am loving this theme alsoThis is the nineHD theme ($2.99) from Cydia. There's an update (v4) on the creator's MacCiti thread: http://www.macciti.com/idevice-art/iphone-4/theme-releases/2833-nine-hd-iphone-4-a.html
I'm really loving this one.