How I did It.
Once you've jailbroken your iPhone, you can download a package called "Zeppelin" off of Cydia.
However, you have to pay for it, if you're tech savvy, you'll know a way around it.
If you don't know or are too lazy, drop me a PM and i'll give you a repo for it.
Once you have that package, you can search "All Car Models Logos" from the Modmyi repository.
It'll give you a massive list of car logos (and more if you want to search for others) to replace as your carrier.
If you don't know how to Jailbreak your iPhone. Go find out.
Without Jailbreaking
You need a mac first off, and an application called Carrier Editor.
A quick Youtube search will more than accommodate you.
Why
I just like to express my love for Renault