Edit: This answer refers to nandroid backups made by a recovery (ex CWM). I think it applies to your case, assuming you do a full backup via adb.
There is at least one unique item that would be duplicated: the Android Device ID. This ID is generated whenever you wipe and install a new rom, but it is preserved with a nandroid backup. This ID is used by some apps to track unique installs or authentication.
Some devices store the MAC address of a network interface in memory (such as the Nook Simple Touch and its wifi interface), not on the chip itself. This makes it even more important to keep an original image. In the case of the nook, many people who rooted it didn't keep a backup of the original, so they lost their original unique MAC address. If your particular device does this as well (it probably doesn't), then you would have major problems if two devices tried to access the same wifi router.
Other than that, I personally have not had an issue with copying a nandroid backup from one phone to another of the same model. I can use Titanium Backup to manually generate a new Android Device ID, and the Optimus V doesn't depend on the rom for any MAC addresses. As long as the phone is fully wiped before restoring a nandroid (and it is the exact same model and chipset), there shouldn't be any problem.