I'm still totally new to all this, so I wouldn't take my opinions with much value. But I still like to get involved :P
Firstly, that is some gorgeous rock, really stunning and the substrate makes it pop so well.
I'lld love to see it tried with two main changes to experiment. I think the two rock arrangements look great, but is there any way to raise the left section up just a little higher? Also with the top down view maybe to shift the left section back a few inches and the right section forward a few inches?
The placement within the clusters looks perfect though and wow again that is some gorgeous looking rock!