I love the idea of please recycle, the execution of the conversion is very well done. I dont think that you have too much green, just not enough contrast like you said. Maybe adding some washes, thraka green/devlan mud into some of that green, then highlighting over it with a different shade of green. same thing for the dead marine getting himself munched on. I find for nurgle metals, base coat of tin bitz, dry brush bolt gun, wash with black/brown, small highlights of chainmail come out looking awesome.