There is about a thousand different ways to do a paludarium. For the background you can use corkbark, tree fern fiber, styrofoam coated with something, great-stuff coated with something, lava rock, etc.
I've done a couple of the stryofoam ones, and I just coated it with an epoxy/sand mix. I've read builds where people have used silicone or drylock, but I don't have any experience with those myself. One of the advantages of treefern fiber or corkbark (and I imagine coir matts as well) is that you can stick mosses and epiphytes on it pretty easy.
For the waterfalls, most of my builds had a built-in filter, usually just a small chamber with a sponge for biomedia, and a powerhead/pump set in the chamber, and a hose/pipe going through the background to the waterfall.
If you haven't, you should take a look over at http://www.dendroboard.com/
It's quite a bit smaller/slower then this site, but there are a lot of threads on various paludarium and vivarium builds, and they are all beautiful. Lot of people with some really good experience and ideas over on that site.
I've done a couple of the stryofoam ones, and I just coated it with an epoxy/sand mix. I've read builds where people have used silicone or drylock, but I don't have any experience with those myself. One of the advantages of treefern fiber or corkbark (and I imagine coir matts as well) is that you can stick mosses and epiphytes on it pretty easy.
For the waterfalls, most of my builds had a built-in filter, usually just a small chamber with a sponge for biomedia, and a powerhead/pump set in the chamber, and a hose/pipe going through the background to the waterfall.
If you haven't, you should take a look over at http://www.dendroboard.com/
It's quite a bit smaller/slower then this site, but there are a lot of threads on various paludarium and vivarium builds, and they are all beautiful. Lot of people with some really good experience and ideas over on that site.