hi there im no real expert at this but here goes !
if it were me who would be setting up the amazon themed tank .. I would probably make the tank a bit acidic, the water being quite stained with tanin i would go for shiny fishes like neon tetras or cardinal tetras I cant give you tips on the plants however because im not familiar with the plants found in the amazon rivers
since it would have to be a bit tannin stained IMO then i would suggest plans tolerant of these conditions, how about anubias species tied to interwinding driftwood ?? just an idea
Ludwigia,amozans,spilanthoides,cabomba,elodea,bacopa,caladium and vallis are all found around the amazon . As Kenneth said alot of the ammazon is a black water area (heavy tannins) but there is white water too.
I dont know if these are found in the amazon but onion bulb plants work well creating the look because the grow up and along the water surface kinda dappling the light, either that or have long pieces of bog wood pointing up the way (siliconed to a pice of slate maybe) with lots of java moss growing on.
What kind of fish do you have in mind for it and what size is it?
I don't know how others feel about this website, but I was led to it by someone at TFF. It is a very informative website that specializes in biotope type aquariums.