Tumbled marble might look out of place if it's the only natural texture in the room. If you want to keep a similar contemporary mosaic, then 2 things for you; Firstly, measure for yourself the actual mosaic sheet - don't take the written dimensions as gospel. Secondly, once you have a couple of favourites in mind, take a look at tile trims to incorporate with the mosaic. Remember, you can cut the mosaic sheets into thinner strips. Trim could be square edge tube style trims or even L shape angle in either aluminium or chrome and can be used at the sides of your mosaic or, in the case of the angle trim, used in multiple vertical lines running through the mosaic. Knowing the dimensions you have to play with will make it easier to design a solution that keeps grout width to appropriate size of 2-3mm for wall tiles.

There are never right and wrong answers to this Cath....it can also become actually more confusing when you're not 100% and you get various/conflicting additional advice/opinions and then have to filter/distill the choices/options/opinions down to a final decision........when all else fails, trust your instinct/heart...you should "know" when it feels right....people sometimes ask why/how have I made a particular decision or move one way or the other, and sometimes my answer is simply "because it feels better that way than the other" - when it comes to design sometimes your "technical head" is your enemy ;)....sure the bench top material could look awesome as a splashback, but for you specifically the blue tile may be the better option, where it started and what you are drawn to......have you considered options such as a grey/earthy bench top? I've seen that done recently on a job (not mine btw) that combined with blue splashback tiles that you wouldn't expect to work on their own, but for what they were going for it was a perfect complimentary match.......when you get stuck with the decisions/palette resolution, sometimes freeing up and considering a lateral option is the answer to moving forward getting the balance and breathing space required

Its going to stick out no matter what you do. Is there no budget to reface the cupboard doors and drawers? My Only Suggestion is to not do a White Gloss and instead use a Ravine laminate or a totally different colour and use the colour somewhere else in the kitchen like the off cuts for a frame for some artwork. Or on the kicks. If its going to stick out, and it will, then go all out. The next best option is go to a joinery company ask if you can take some off cuts out of the bin, make a temporary shelf and save up so you can do everything at the one time. If you redo the kitchen you will end up redoing that cabinet to get a consistent colour. Even with colour matching there is still slight differences because one is new and the other is old.

Proportional consistency - keeping the 1:2 rule in place everywhere will jar less than having the same architrave but varying the skirting. If you’re already considering 90 and 140 skirting, why not go for 40 and 70 architraves? The effect will be more harmonious and it shouldn’t impact the price too much ... plus, it’s your house - if you like the 1:2 rule then use it :-) (PS: if it does impact the price too much, just pick one size of each and save more cash)