hey Nick-There's someone here who used bubinga in their shower. Look about halfway down and they (pharaoh) explains what they did. I don't think they (he/she) would mind if I shared this lovely bathroom:

Here is a link that might be useful: pharaoh's bathroom

Tigerwood looks like a good choice for a bathroom application. Have you looked at ipe? It is denser (by far) and its resistance to rot and decay is second to none. My shower floor is natural ipe (it doesn't need to be treated), no problems. We bought a few pieces of ipe decking and diy'ed the floor. But other woods will work as well, although they may need to be treated as pharaoh did with the gorgeous bubinga. I'm planning a second bathroom with wood in the shower, I might use cedar, not sure yet.

I should add that my only experience is with removable (for cleaning or sanding) wood on shower floors. Permanent wood on the wall is likely more challenging, hopefully pharaoh chimes in.