These weddings usually come with a planner, a banquet manager and a run sheet, and the wall needs a line on it. Where we are told the schedule we install cleanly around the room flip and nobody notices us. Where we are booked late and slotted in, we are one more van in a service corridor already holding a florist, a band and a cake. Early is better, and it costs nothing.
For the historic venues in town the honest answer is sometimes that the wall should be smaller than you first pictured. A room with period detail and a lower ceiling does more for a photograph than a wall that fills it edge to edge, and we would rather say that when you enquire than build something that overwhelms the room you chose.