Live plants would be nice, but if you can't or don't want to, I think you can make fake stuff look alright. Beautiful fish by the way. I would definately ge some plants of different height, also you have them all in a row along the back. Try to move a couple up to the front and some to the middle, as long as that would accomodate your fishs' swimming (I don't know anything about discus. Also some more rocks might be nice and maybe a cave or hiding spot of some sort? You could situate a few plants around the cave.
