The more plants, the better! You definitely have a good start, but these little guys love to hide behind leaves and climb around on branches. You can't go wrong with plenty of horizontal branches and leaves for cover. Live plants are really helpful to keep humidity up, but there is nothing wrong with the synthetic ones like you have going through there for cover.
Good call with the branch across the top in the middle for basking. I also have a thick vine that loops around the bottom because I noticed that my guy likes to walk down and poo in the morning hahaha Throw some more branches and leaves in there, and you'll be good.
The waterfall you suggested won't really be helpful... it would most likely just breed bacteria more than add benefit. Chameleons don't drink from standing sources anyways. To keep the humidity up and provide hydration, regular misting (with hand mister a lot or with a timed misting system) is your best bet. The live plants help to hold the humidity, as well. Some closed sides are beneficial; I cut up a plastic shower curtain and attached it over three sides of my enclosure, and it helps a LOT. I also keep a humidifier going in the room that I keep my cham in during dry winter months.
I see you have a paper towel down on the bottom... that may just end up being more annoying than anything. I tried it with my first cham. It lasted about 36 hours. Having a sort of drainage system in place is the easiest thing to deal with. For my first one, I had the cage set up on blocks, a few holes drilled in the bottom, and a plastic container under the holes that I emptied every other day. I have definitely upgraded since then! Mostly thanks to my crafty carpenter dad hahaha to clean up the bottom of the cage then, I was just able to wipe up anything on the bottom daily and disinfect on a regular basis.
Anyways, you are definitely on the right track. Rock on and good luck!