there are two ways you can do this
1. in customize go down to SpringBoard String
the other is a more free way to change text, like on mine when it syncs my iPod I have changed it so on screen it will say Syncing iPod Touch instead of just Syncing iPod
now I wouldn't reccomend this route unless you knew what you were doing....... and dont forget always make a backup before you do anything.
2. you need to go to /System/Library/CoreServices/SpringBoard.app/<language of choice>.lproj
(dont look for a folder saying language of choice lol that just means if your ipod is in french then french.lproj etc)
in their will be a file called SpringBoard.strings (open this in a text editor), only make changed that you need to dont delete lines or anything. Best way to find what you need to change is to see how it appears on the touch's screen and then to search the file for how it appears and change accordingly