There should be an official list of things banned by the eighth amendment. While the founders wrote the Constitution with justifiable room for interpretation, there is too much room for the heart to get in the way here. If an individual is too personally involved in a case or particular horrendous topic, he or she might not view anything as too cruel or unusual to use as a punishment.
Yes, there should be an official list of punishments that are banned by the 8th Amendment, because the Supreme Court establishes the list, one by one. As these cases are taken to the Supreme Court, one by one, we have a definitive list regarding the limits of the 8th Amendment.
I do not think that there should be an official list of punishments that are banned by the 8th Amendment. I think that the government should be able to decide just exactly what type of punishments are appropriate for certain cases. I also think that it is something that should be done as long as the people of the USA support it.
If there is a question as to the legality of a certain punishment, then that needs to be taken up within the legal system when that punishment is handed down. Most states have legal minimum sentences for certain offenses. That list itself prescribes what punishments are meted out for crimes, which obviates the need for a list of punishments banned by the Eighth Amendment.