It's been quite a while since I was at the Morikami Museum. And although I have always wanted a Japanese garden (and a private dojo, for that matter) it won't fit with my married life.
At any rate, I can probably answer your questions on specific plants as I am initially from S. florida.
On the pictures - when you go to post, have your files hosted somewhere else (like uploadit.com or whatever) then hit the IMG button, put in the URL of the image, and hit the IMG button again.
Bamboo - most people practically ignore it and the stuff just grows. Maybe you are watering it too often? This is a plant you have to maintain else it spreads and will turn your 7x7 space into a bamboo forest. I'd keep it in a pot, or inset in a boxed space in the ground. I hear it is a pain in the kiester to thin out.
My personal opinion: japanese gardens, loosely, are a place for you to be happy and relax. I would pick plants that give you that feeling. If you like amaryllis, I'd use it.
My Japanese is pathetic - but if I recal - chisai means small, so what is kame?