I love the 'scape's concept. In particular, the image of a distant mountainscape.
When I first saw it, I thought it was perfect. In a "don't change a thing" kind-of-way.
But since you asked for a critique, I'd say the 'scape could benefit from one more sharp, pointed rock angled upwards towards the center (to just below the seven o'clock position of the basketball). The rock I'm seeing in my mind's eye is very specific, however, and it's kind of a tall order for you to get that exact one. I guess what I'm trying to say is that the jagginess of the rocks you chose is what sets it apart from other Iwagumis I've seen.
Other than that, I think it would be better-served with Aqua Soil Powder, but if you're going for a carpet, that point is moot.
Do you have photos of the other rocks you have to work with?
EDIT: Here's a 'scape that's reminiscent of your layout.