There have been extensive posts and threads of good vegetation to plant. My two favorites are a corkscrew eel grass and American pondweed. The lilies would provide some benefits, but be careful they aren't invasive and take your pond over. Sinking cedars in 3'-6' of water in dense bunchings of 2-3 large trees or 4-6 medium trees would be most beneficial in my opinion if you are looking for non living cover. Tight cover which excludes bigger fish is key. You want to let your GSH in, but keep the bass out.
