I'd suggest watching your betta to see what his personality is like. Mine, for example, loves tunnels and anything he can swim through. I've got my eye on a terra cotta pot with the bottom removed or one of those great floating logs from zoo med: PetWise Market - Zoo Med Floating Aquarium Log - Small
Some like to hide or have things to swim in and out of, so the java moss is great...maybe some more plants or hiding places would be good too. Broad leafed plants are good because some bettas like to rest on the leaves.
Here's a great website that has suggestions for betta environments: Bored Betta? - UltimateBettas
Good luck...he's a beauty!!
(hopefully not offending you by assuming you're not familiar with bettas...I can see you are very experienced in this hobby...Just so eager to be helpful now that I'm somewhat
less of a newbie)