It's looking great! I love the rocks and the overall layout. I like the idea of some Anubias in there for contrast. Maybe a Nuphar japonica, the large, light green, translucent leaves would be a great foil for your spiky plants and it's easy to train it to stay a certain height.
The Ranunculus inundates is great (I think it may be what I traded to Robert). Mine always heads toward the back of the aquarium since the tank is in front of a window and it wanted the sunlight - darn plant ignoring my scaping plans.
Anyway, as long as it gets sufficient light it's easy to grow.