Have not tried and I had to look up what a ceramic garden stool is. You absolutely DO NOT want to use this in your shower. If you must have a stool in your shower, it should be either permanently built in or specifically designed for use in a shower so it can never move around when in use. It feeling hot or cold will be the least of your worries.

[sorry for the duplicate images.]

It would only work to use the garden stool if it's just a storage device like in the photos posted above by bluenan. If you intend to use it for sitting or leg shaving, it's not a safe option.

They make teak shower benches that can stay in the shower. You just have to make sure there's enough room for either.

Most of the shower stools I came across are teak, but I wanted to get away from that look. Do you think the ceramic stool would slip on slate tile flooring?

The ones I have are unglazed on the bottom and not slippery at all. You could always put it in a corner.

I really would like to put a ceramic garden stool in the shower but I can’t think of a way to cushion its unglazed base so that it doesn’t scratch the shower tiles. Chair felt pads would loosen with water......

Not sure why people keep saying this wouldn't be safe. Why wouldn't it be safe?

@Kenny--I think people are worried about possible slippage, but that has not been my experience.