OK... aesthetic, natural-looking, opaque, waterproof.
By coco liner, I take it you mean this stuff that comes in a roll vs. loose that you glue on like in Clint's video.
View attachment 270204
vs.
DIY BIOACTIVE ENCLOSURE | Step By Step With Links
- Would cork (roll, tiles, or backdrop) be a viable alternative?
- Vinyl backdrop? I've seen some that are printed like a rainforest, only vinyl, so misting won't harm them. I've also seen peel & stick textured vinyl backsplash—looks like ceramic or stone, but far less expensive.
- Fabric—like a rainforest batik, stretched & waterproofed.
- I've seen some creative things done with (plastic grid) egg crate.
- Aquarium backgrounds (at least they're waterproof!

- And the old standby—sculpted styrofoam. More labor-intensive, but almost limitless options & creativity. Similar to spray foam. I might start with a thicker piece (2-3") or layer pieces of ½" to 1" to build up some areas, but not others, then sculpt.
Obviously some of these ideas could amount to more than you want to spend, but I'm just brainstorming OTTOMH, so I put cost on a back burner
at first. Sometimes there are less expensive ways of doing something that
looks more expensive.
Another way I approach brainstorming is doing a google search for say... chameleon enclosures—to find & collect ideas I like the look of (in some kind of file: PowerPoint, OneNote, a collection of JPGs, etc.) then figure out how to achieve what I like for le$$.
I hope there may be something here that's useful, or at least stimulate your imagination. ?