Shower niches are open to the air for a reason. Enclosed damp space = mold. NOT a good idea.

hollysprings - yes, I am well aware of that. I'm looking for the best of both - sufficiently drained/ventilated and still "hidden" space for clutter or unsightly stuff.

Perhaps the vertical front "wall" of this space could be vertical slats, allowing air and water to circulate. Or perhaps a little tiled "riser", but that doesn't go all the way to the floor - leaving an opening for air and water to flow through.

I suspect this must have been done by somebody. I'm hoping someone has seen examples.

I've seen that space utilized from OUTSIDE the shower via an ordinary cabinet door, and thought that was very clever.

But accessible from inside the shower? A perforated metal panel might work, but wouldn't be too friendly for mid-shower use. Sliding door tracks would get nasty-gunky pretty fast, and hinges would probably collect hard-water deposits like nobody's business...

What about leaving the under-seat area open and storing your 'ugly stuff' in some attractive baskets that stash away there? I've seen some nice-looking plastic baskets with open-work sides -- just drill a few more holes into the bottom and you'd be good to go.

we don't have closed storage but I put a corner teak seat in our shower. Signature Hardware sells one
http://www.signaturehardware.com/product17864?origin=product-search&cvsfa=589&cvsfe=2&cvsfhu=333038313834
we have had it about 2 months and it looks great. The great advantage to a teak seat over stone or tile like your shower walls is that it isn't cold! I actually sit on it while I never sat on my stone in a previous house because it was icy.
The other thing i do to keep all the ugly bottles out of my beautiful new shower is that I keep the things I only use some of the time in a plastic crate in a drawer and I pull it out when I need it and put at the shower door. When i'm done, I just put it away.

Teak slats is what came to my mind. I have never seen a design. I wonder if there would be something in the world of pools? To open a door/seat means hinges. Hinges and water; not sure how that would hold up. At my house the bathroom is used by five people. Not having what you need in the shower means a lot of dripping across the floor to get what you need out of the cupboard AFTER you already began your shower. For us a caddy stored elsewhere is not practical AT ALL!

Storage under a bench is too low to the floor and would pose a slip and fall hazard.

Re hinges - it should be possible to get stainless steel hinges. Or brass. Either should work reliably. If worse comes to worse, should be available as boat parts. (Even more expensive that bath parts.)

Re storage is too low - how is this different than picking up the stuff that falls out of a niche? (And it does, at least for me.) In any case, I would expect to have one or more niches as well for the most commonly used stuff.

Interesting that so far nobody has actually seen a picture of anything like this. I can't be the first to want it.

Here are a couple of pics:

I really like the idea, if something could be worked out. I've seen a lot of slatted teak planters and tables meant for outdoor garden use and I'm wondering something like them might work in a shower. My preference would be an open tiled bench, with a slatted teak bin/basket sort of thing that fits under it. The advantage being that it could be relatively easily replaced when and if it gets disgusting.

olychick - interesting, but I'm not sure I understand what I am seeing, expecially in the 2nd pic. The first seems to have an opening, like an alcove or niche, under the seat. I can't tell - it almost looks like it has a glass front. If so that makes no sense to me.

The 2nd I totally don't understand, unless it was taken before work was complete. I don't see any glass walls. So it looks entirely open. The "seat" does look interesting if it is open. The storage wold seem to be accessed from the outside. Or maybe that is hiding space for shutoff controls. In any case that wouldn't work for me.

Melissa - now that you mention that, it does sound like a good way to go. That way the seat is fixed with no moving parts to break. And as you say, the bin could be replaced. And it could still look good. Thanks for that idea!

how about some stainless steel baskets? wire mesh type of thing?