A niche is a waterproofing detail, not just a shelf
A recessed niche is essentially a box built into the wall cavity, which means every interior surface of that box, not just the shower's flat walls, needs the same waterproofing treatment the rest of the shower gets.
A niche added as an afterthought, cut into an already-waterproofed wall, is far riskier than one planned from the framing stage, since retrofitting waterproofing into a small recessed box is harder to do completely than treating it as part of the original membrane.
Placement and blocking
Niches are typically framed between existing studs to avoid cutting structural framing, which is part of why niche placement should be decided before walls are closed up rather than requested mid-project.
A niche placed at a comfortable reach height, roughly between shoulder and waist height for the primary user, gets used far more than one placed purely for visual symmetry with the shower's tile pattern.
Lighting inside or above a shower
A light fixture installed inside or directly above a shower enclosure sits in one of the wettest spots in the home, and fixtures sold for bathroom use are rated for different moisture exposure levels, typically labeled for damp or wet locations by the fixture's own listing.
Ask your electrician which rating a specific fixture carries and where it's rated to install, rather than assuming any bathroom-labeled fixture is appropriate directly inside a shower enclosure.
Planning niches and lighting together
If a niche and a light fixture are both planned for the same shower, decide on both before framing starts, since running electrical to a fixture location and waterproofing a niche box both depend on the wall being open at the same stage of the job.
A recessed light directly above a niche can make it easier to actually find and read a shampoo bottle, a small practical win that's simple to plan for during a renovation and difficult to add gracefully afterward.
Sizing more than one niche
A single wide niche is generally easier to waterproof correctly than two or three small ones scattered across different walls, since each opening is another set of corners and edges that need careful membrane work.
If more than one household member uses the shower regularly, a second niche at a different height is a reasonable request, but weigh that against the added framing and waterproofing complexity before assuming more storage is automatically worth it.
A practical planning order
Settle on the wall material and waterproofing method first, since both affect how a niche's interior gets finished and sealed.
Settle on niche placement and any light fixture location next, while the wall is still open, so an electrician and a waterproofing installer aren't working around each other's finished work.
Confirm both in writing on the final plan before tile or panels go up, since this is the point past which either detail becomes expensive to change.