Wow. I love this. Take it from me, I'm a huge Iwagumi scale fan, and I'd consider my Iwagumi a success (see signature), that this is perfect just as it stands. What's important now is what it will be planted with. Remember, the rocks/hardscape are ony half the story you're trying to tell here, half the picture to paint.
I would suggest HC as a carpet plant, Blyxa japonica just behind the stone(s), and something like DHG along the back wall and possibly some of the sides. Very straightforward, traditional Iwagumi, but perfectly so. Great job with this tank, can't wait to see it develop.
"Simplicity is the ultimate sophistication." -- Steve Jobs