Heres a custom theme I made for my iPod Touch, I pretty much recreated alot of the icons from the game for the springboard icons and made some myself. It has custom locking, slide-to-unlock, typing, charging sounds aswell. It's not ready to be released on Cydia yet because I still gotta make a new keyboard as well as more sounds/icons.

All the Gran Turismo fans out there like me will go crazy for this theme :D

The theme is created by me

Apple iPod is copyright Apple
Gran Turismo is copyright Polyphony Digital