If you have a shelf next to it I would get rid of the niche entirely.

I can't tell from what you said if you really need it. If you don't, don't bother. If you need a small one, just 9 -12" wide should do. Use the size of the tile and how it's laid out to help you decide what is the logical/best size.

Thanks for the suggestions. The niche has already been built so the only thing I can do now is shrink it. I do think I want a niche not just a shelf since the shelf is quite small and the shelf will be visible from outside (unlike the niche which is partially tucked) so I want the shelf to remain without product. It will be used for propping up a leg to shave or to put a product temporarily on it. The niche currently is 28 inches - way too long!! The height is also 15 high - thinking of shrinking it to 13 high.

Update: Currently thinking 23 long niche - generous space but now 5 inches shorter.

Only you can guess what products you will want in there, but I would like to warn you of the danger of discovering that fuzzy hair just might be wavy or curly. I now have multiple products resting on my grab bars that make that happen for me. If this is a family shower, you can’t go wrong having extra room for someone who needs a moisturizing shower wash, who discovers a product-intense hair trend, or some future need for shower storage that we can’t yet imagine. My moisturizing shower wash has a pump top that might not fit well in 13” height.

I dislike shower niches and for sure done in aaccent tile . Why not just get a nice shower caddy . I do not know what you mean by the niche is already there . That appaerently is the gist of the question . I always try to talk my clients out of niches there is IMO no reasn to make shampoo bottles the star of the bathroom decor. We have Internationl students they share a bathroom and just bring the stuff they need for the bathroom in a little bin I supply no need for a niche and makes cleaning the shower so much easier too. I have also found it a leak occurs it almost always starts with the niche.

I would leave as is.

Got pictures?

Because a 12x12x17 shelf in a 3x4 shower has me questioning if there is adequate room left for bodies...

A niche on the backside of a kneewall is NOT shampoo on display. C'mon, PCC!

Leave the niche big. It's better than the alternative (which is NOT schlepping shampoo to the shower every day but instead is too small a niche).

I would pull out the shower products you and your husband use and see how much space they take up and use that to guide what size is right for you. If you and your husband use the same products in small bottles, a smaller niche will probably be just fine. If you buy large bottles or each use an array of products, you'll need something bigger. But personally I'd rather have a niche that's a little too big than one that's too small.

I would never accept a shower designed without somewhere to put products, and ideally not positioned to be a visual feature. Not all niches are design elements. They serve a function for the user. On a side wall a niche tucks the products into the wall out of site unlike a shelf that protrudes. And I cannot imagine as an adult in my own home having to shlep a caddy of products to and from the shower like a student in a dorm with a shared bathroom. No thank you.

We had a niche in a knee wall. Loved it since it was not visible from outside the shower! I’d want it big as long as it’s far enough away from water…

I decided to reduce the size of niche so that is doesn't overwhelm the small space. Now it is 22 1/2 after tiling which allows for about 6 bottles - enough for both myself (4 bottles for myself, 1 shared body wash) and spouse (1 shampoo bottle!). It is the perfect size for us. The height is 14 1/2 after tiling leaving plenty of room for larger bottles.

My niche is 4’ wide in a six foot shower…