Very pretty! How is the waterfall flowing? (I can see now that when I said it looks like a bridge, I was looking at it the wrong way. It had seemed that there was a hollow under the riverbed.)
In terms of arthrodpods, no idea. For vivariums, you could do tropical types of cockroaches, perhaps a different morph of isopods, millipedes, blue death feigning beetle, mantids(depend on species), giant vinegaroon, scorpions like an emperor.
If you were setting up the vivarium just for the arthropods, then the following make great pets:
Tailless whipscorpions /ambliplygy(Damon diadema, Paraphrynus cubensis) (they tend to like it on the drier side with lots of vertical objects to hang onto, I saw an amazing setup like this at a zoo, and had success breeding them myself with a similar setup, they're also communal so it can be great to watch them interact)
Centipedes, could do a nice setup with scolopendra polymorpha or S. subspinipes, tropical plants, etc.
I was wondering if there were any other beetles that work well with a planted environment, like stag / rhino / hercules beetles?
I took a class in Yucatan once, part of which involved being in a tremendously uncivilized neck of the woods --- probably no electricity in a 75 mile radius from it. It was very much a tropical wooded environment, and there were creepy-crawlies out the wazoo. Once at night, I heard what sounded like a little helicopter flying around me. The next day when I described it, one of the guides said they knew what it was, and he showed me the corpse of a 6" beetle.
I doubt 6" beetles are exactly a norm in the insect pet world, but that's just an example.