I think I created a monster-suggestions please

[faraway]

.... I know I can get a backdrop with trees but have not seen one with a river that runs horizontally which I would need to tie into the area with the car float.

Ah, I assumed your track plan drawing is upside down posted and the car float is in the foreground. You have the car float in the very rear of the layout and need a matching background.
What if there are industry buildings behind the car float too because the the car float is in a basin that attaches to the left into the river? Otherwise would you need trees, river and the other side of the river too. I guess the river would not be visible if you stand at the ground on this side. But the river became visible from an elevated standpoint like your when operating the layout. That is a very difficult situation I would try to avoid. Put the car float in a basin surrounded at three sides by industry (foreground and right side layout, rear side backdrop) and the open river at the left.