I started by cutting up an old backdrop in two different heights, 20cm and 8cm.

I cut the edges in an angle so that the sand will cover most of the edges, and used silicon to glue coconut "hair" on them, to make it look better. I also put silikon on top of the coconut "hair" to seal it in just in case it rots after a while.

I then made some caves, and cut holes through the pieces witch I pushed the caves through. I sealed the holes with silicon on the backside to prevent sand leaking through later.

Tje caves are of various sizes, and I also used a round glass vase just in case somebody would want to use a round cave. All the caves will be covered in sand, so hopefully even the glass one will feel safe enough to use...

I will mount a 3D backdrop later, as soon as it gets here in the mail, and I will use expanded polyester to fill up the largest terrace so I don't have to put 20cm of sand in there.. I will also use silicon to seal all the edges side and bottom so that the sand doesn't leak down to the next level.
Did I overlook something that could cause problems with this setup later? Any ideas on how to complete this setup so that it will work and look the best possible way?