If your wainscot is tile then it can serve a dual purpose by working as the backsplash behind your sink.
Should wall tile be as high as the sinl.
A classic offset or straight set pattern in a standard field size tile works best for this wall height.
But only if it is high enough.
Besides i always prefer to transition materials on an inside corner wherever possible and this is the perfect place to do so.
I am planning on taking the subway tile backsplash up to the ceiling above the window by the kitchen sink which is an 8 ft wall that meets the slant.
Take wall hangings and mirrors into consideration.
Plus that height kept the very wallpaper we hung above the marble safely away from splashing water.
The main wall of my kitchen is 11 5 ft tall.
If you have a feature wall with a window and bespoke joinery and you are using a feature tile you may feel that you need to find a suitable cut off point.
I did marble tile to 48 in powder room.
The wall of tile you re doing over the sink area will be a nice statement and has a more high end look.
For a truly classic look finish the top with a decorative trim or a bullnosed edge.
600mm high is usually a good rule of thumb and finishing at the low part of the cabinetry ensures that you maintain the height of the ceiling.
Tiling the side walls will sort of take away or diminish the impact of the back tiled wall.