We have been on Regent a few times at Christmas. Decorations in common areas and at entry into dining rooms, but I don't remember anything on our individual tables or in the suites. We almost always buy flowers on shore before boarding the ship, to decorate our stateroom. Cruise lines often provide some type of flowers in the suites, but we like BIG seasonal flowers on our tables. We also bring small seasonal decorations, table clothes etc to decorate under or around our flowers. We like our space to be festive. Often our room stewards want our decorations for their rooms when we leave the cruise.
The big holiday question for us is will they have eggnog! I have made a special request in the past and they figure out how to make it in about 24 hours!