Looking at your competition entry, there didn't appear to be any effort put into basic aquascaping.
There's no argument that your plants looked healthy, but it looked like everything, (and I mean everything), was in the centre of the tank...and that's where you'd expect to find the fish to display themselves.
A black background, as already suggested, would help things 'pop' immensely.
Now looking at that Vallis (?) or Sagittaria (?), if that was to each side, you'd have your plastic pipe and filter hidden from view.
A possible Show Piece plant could be that good-looking Madagascar lace, but's overwhelmed by the rest.