Nice start Storm. I think your stone layout needs a focal point. It seems kind of spread out right now. My eyes doesn't know which stone to focus on. Check out this article on Iwagumi by ADG Frank. It might help give you some ideas on how you want to layout your stone. Oh...and where and how are you going to hide your filter?
ADG Frank's Iwagumi Article
Edit: Here's a couple more Iwagumi articles.