Using Carreaux de platre - "Plaster tiles"

[Araucaria]

We're putting a bath against the longer wall of a bathroom - the bath will be about 60cm shorter than the wall.

Our tiler has said it's best to make what would otherwise be the bath panel out of "carreaux de platre": effectively build a small wall under the edge of the bath, and then tile it (leaving a trappe de visite).

I've bought the tiles ready for him to do his bit - they are 66cm long, 50cm high, and 7cm thick (and they are the "hydrofuge" ones too).

My question is about what I can do with that extra 60cms. I'd like to have a tiled surface at the end of the bath, perhaps with a small (60cm wide) cubby-hole underneath it, for towels or bottles of shampoo or whatever. The cubby hole would go back towards the wall the width of the bath, or maybe a bit less as it will otherwise be hard to reach into it.

The plaster tiles feel fairly strong but they are clearly also quite fragile: I am sure a good tap with a hammer will shatter them. Are they suitable for making the "worktop" tiled surface, over the top of the cubby-hole? I just have in my mind the feeling that one day someone will see this nice tiled surface by the bath and decide it's strong enough to stand on - or sit on - and it will then disintegrate.

I also wonder - if we do use the plaster tile for the surface - whether we'd then need to tile under it as well as on top. It's a rather chalky surface. Can it simply be painted over instead?

You'll have gathered by now I've never seen these things used before! Advice would certainly be welcome.