Depending on your taste of course, I would introduce some colour - either as tiles or a glass splashback. Personally I think you will need to fill the entire area otherwise there are simply more lines to take in and will create an unwanted feature. We've had a glass splashback painted back and it was super easy to clean. For one kitchen, we've gone for a bright yellow to give it some pop. You can also have photos too but it's not as easy as the file sizes mean that they need to be taken/supplied by a professional photographer. If tiles is your preference, there are many great patterned tiles out now. Good luck!

To be a voice of dissent, have you considered soft greens or green-grey? I've got Baltic Pine floors, pine cabinetry, stainless steel appliances, and black tiles in a BRIGHT west-facing kitchen. I went with Taubmans Swiss Meadow double strength and it compliments all the different elements. If you don't want something "obviously" green, check out Taubmans Alpine Snow (double) - it seems to change colour in different light. It's a pale green in full daylight, but looks soft grey at night.

I love those benches I have used one as sewing/desk with trestle legs, love it. The following is my idea with timber bench tops and using your cabinets, This would work if you could run the plumbing across to the left,either inside or externally. ,I have moved the sink to allow you to use the 80cm cabinet as your dish rack, the window won;t allow this. Or you could just swap the sink and cooker and use other shelving for the dish rack Back wall R-L 60cm cabinet,cooker,60cm cabinet 800 void for sink,60cm cabinet.fridge. Wall, using the 80cm x 42cm as plate drainer with timber open shelves on both sides, extraction is a simple ceiling extractor fan. I have added a narrow 60cm Island which uses both 40cm at both ends,like the sink there's a void which can have a couple of stools andr rubbish binscan be placed under the sink cheers

custom made vanity and wall cabinets should only be needed if you have awkward sizes as an off the shelf cabinet allows you to see and touch the product and is often much more economical than custom made ...unless you need to keep some special supplies (eg 24 pack of toilet rolls?) i suggest that a base cabinet need only be 450-500 deep which is plenty for folded towels and drawers and the in wall cabinet about 150mm deep (including most of the cabinet inside the wall and only a small frame for doors and mirrors projecting out) but the in wall cabinet may depend on existing wall studs and electrical wiring so think about what you would put inside the cabinets and only have enough inside cabinet space for those items (maximum toilet roll or fat shampoo bottle about 120mm...in small bathrooms the extra floor space makes drying and dresssing much more comfortable and by rotating the shower in the family bathroom there would be less wet floor in the walkway and if the vanity in the ensuite is away from the corner you can allow space for a handtowel and/or a very convenient space to hang a hair dryer ...