Looks great! I'm always happy when Bettas are given a proper home instead of tiny bowls. Make sure to post pictures when you have your new plants. Also, you could add a group of small corys (pygmies, dwarf, panda) to give your betta some company (but this is just a personal preference).
Wow... that's a loooot of gravel!! Not in a bad way, tho. Man, he must be lovin' it in there!! But I agree that he might enjoy some tank mates... and they'd help keep the tank cleaner, too!
Yep that's hornwort. I'll eventually add some tank mates, I'll probably start with a shrimp or two to make sure he's not too aggressive towards other critters.