What should I do if the wedding ceremony of the couple is not arranged according to the previous design due to the upgrade of hotel decoration?

It depends on when you negotiated. If it is before the hotel upgrade, you can discuss with the hotel to see if they can try their best to achieve your satisfaction. Although it may not be what you asked before, try to make you feel acceptable. Let's negotiate. After all, marriage is a lifetime thing. Don't let it affect your mood, but try to be accepted.