a good foreground plant would be something like dwarf sag., towards the back you could have things like swords and stems
you would want quite a bit of wood, root like bits would look good in an amazon themed
rocks if you want, .. a finer substrate also if you were wanting things like corys
any plans for stocking as well?
scaping it you could try and do something like a secluded/sheltered spot in a river, like the scape kind of running from a corner, a fair bit of substrate visible then a few spots of plants in that?...