To me this sort of decision has to be partly informed by how much of the tile will have to be cut and how good your tile setter is at cutting tile. For me, if doing all these accents means a lot of tile with cut edges I would be hesitant. I don't like the way cut edges of tile look out in the middle of the field, and the use of accents and of standard niches for that matter usually mean there is a lot of cutting of tiles to fit in the accent tiles. Does this make sense? But I won't (voluntarily) use standard niches that require tiles to be cut around the niche, either. I will figure out what size the niche has to be to be surrounded by all full tile with bullnose. It's a pain. And it can't be done with a typical subway layout because brick patterns always require a cut tile for every full tile at the end of a run anyway. (I am on the lookout for the company that offers 3x3 standard to make the half-tile for their standard 6x3 layout. I just finished a bathroom that has about 12 fully "cut" tiles, and one row of slightly shaved tiles in the whole bathroom--and it's 2x2 tile. The plan was to have the entire bathroom be 100% full tiles, and we didn't quite make it. And I stare at the row of shaved tiles when I am taking a shower. But this isn't really answering your question. I personally don't think a bathroom with that many sizes of tile even if they were all the same color would look bland or sterile. I think if you start to "accent" too many things, it's no longer an accent. I would be against too many accent areas if it wreaked havoc with the overall tile layout. Nothing personal against decorative painters, I nearly got an MFA in painting as my alternate degree instead of interior design as my alternate degree, but having known some and having been in the houses of some (and having unearthed some of the paint combinations covered up by staging-khaki paint in a house Owned by one: My impression is that a lot of decorative painters don't know when to stop and someone has to tell them when to stop--and this isn't always easy when they are on a design job. But really, if I had a decorative painter in my house, I would want the bathroom tile to be all white and I would want the decorative painter to Paint the walls in a mural or something decorative.

Thank you so much, @kmcg123 ! It looks awesome! Your herringbone tiles are 3x6in, right? We were going to try it with 4x8in herringbone and 4x16in subway brick to save a little money on the labor since our shower is 6x4ft. I was hoping since it's a larger space and the same ratio it would turn out ok! Fingers crossed, it will still look this good! At what height did you start your chair rail?

Try a 1/3 offset. Occasionally that works out better. Hardie backer is not waterproof. Be sure to cover the remaining exposed areas. It appears from your photo to be a lack of fasteners on the left wall. Studs can't be more than 16" o.c. Your professional did not leave you with a tile ready substrate.

@Patricia Colwell most likely the niche will be on the right hand wall in the big shower or we will keep the low ledge so all the items are not directly displayed when looking into the room. the model has a super high ledge, ours is about the height of a standard tub edge. for the stall upstairs shower we arent set which wall. its a metal framed home so its where ever one could fit and if it cant we may do a stack of a few corner shelves next to the facet and shower head. also that smaller shower is in a side 'hall' so when you look into the bathroom its to the side. here is a Pic of the layout in the model. you don't see in the shower unless you are using the toilet or getting in it. I hate caddies cause they never stay together or end up rusting. plus i dont want more things taking up room in the shower itself.