I've done a couple paludariums in the past using stryofoam/epoxy.
I just worked a few pockets into the design for some plants, and also went with some creeping vine types (creeping ficus worked well, ivy, etc.), as well as some that just had bare roots in the water, or emmersed aquarium plants.
I've also done panels of cork and tree fern fiber, and then just jam some sphagnum/substrate in a pocket/crevice with a small plant.
As to water, I had most near waterfalls, or close enough to the water level that they would wick some up.