Quite depressing looking at all those photo's. But I have figured out a lot of them had black side cloths with silver ribbon trim in various designs - some as a square, so that fits, and the black horse plumes were a tradition too, but most of what I see in photo's they are all too long and showy compared to what I saw then.
It could have been a brewery drey cart re-purposed for a funeral as I first thought too. Most of the early ones were flat bed and I have seen most had writing along the sides.