I actually think it tends to make things look clean and crisp instead of busy, I find patterns on white look busier than on gray.
That said, I just made a wedding cake last month that was everything I hate about cakes. Two yellow lily cascades, little flowers all over the cake, bows, pearls and ribbon all in orange and pink.
She gave me a super detailed sketch, and cried when she saw it she was so happy, (I almost cried for a totally different reason, lol.)
If I have a client that has such detailed requests, I never try to change them, especially for a bride. No matter how tactful, there's very rarely a nice way of saying, "you're idea will look ugly."