Nice tank and setup. I like the way you arranged your plants, contrasting heights, created alot of depth.
To hide the pipes behind, you could tie moss to various stick(DW leftovers) and mess. Let them grow a little then tie or hang them on the pipes.
it could be something like what you did with the DW in the middle, but instead of on the substrate, you could hang them on the pipes. Diferent moss arrange together will create an interesting effect also.
Enjoy your arts.