I whipped these up and look pretty cool installed. They can obviously work for any carrier simply name them as follows:
FSO_CARRIER_<carrier name>.png
Default_CARRIER_<carrier name>.png
So for AT&T they would be named FSO_CARRIER_ATT.png and Default_CARRIER_ATT.png and placed in /System/Library/Carrier Bundles/ATT_US.bundle
Files:
