In addition to replacing a tub with a shower and making it all match the old tile, I also added a tall niche in the corner next to the bench seat. These features can be tedious to add to a shower project because there are a lot of tiles to cut and it needs to fit into the greater pattern to look right.
One principle I have for adding niches is to add the shelves later in the process, if possible, so that I can make sure the shelves align perfectly with the grout lines. This niche would be one tall cavity about 48″ tall that would include two additional shelves. To make sure the shelves were correctly placed, and make it easier to waterproof, I built the niche as one large niche using Kerdiboard and then waterproofed the joints and corners.
My laser level is one indispensable tool that I use throughout every tile project. In this case, I could make sure the new tile would perfectly align with the old. It also helped me place the shelves. I tiled up to where the shelves needed to be, then I made a simple shelf out of two pieces of 1/2″ Kerdiboard sandwiched together. This is thick enough that I can tile the front edge and plenty strong to hold a few shampoo bottles. The photo (above) shows part of the process.