I did this for a winter wedding few years ago. Dress from monsoon, was a thick dress, iyswim not floaty/summery, just above the knee in a bright colour with black opaque tights and shoes that matched the dress.
There are some gorgeous dark winter florals about at the moment, either a skirt or a dress with some dark tights and pointy flats will look gorgeous.
Or a dark floral blouse with a pair of wide legged trousers would look fab. Browns and purples are beginning to look luxurious again and don't look like workwear so are a good option if you like and suit them.
Yes, dark florals. I went to a wedding in October and wore a black long sleeved (but floaty) midi dress with a floral pattern in pinks and purples, black opaques, black heels, tweed jacket, black bag and a purple felt hat.