I agree with you the pillars are unfortunate. The replacement tiles will stand out no matter how close they come to matching so you're better off making sure they are clearly different so the gray one is better. Putting busy mosaic tiles could look nice but will interrupt the flow between rooms which I'm guessing is your problem with the columns in the first place. You will need to create a dextrous solution to tying into the 2x4 wall on the left side but I think it can be done tastefully- maybe beveling it back once you get past he end of that wall.

Lighting - pendants over the servery bench should be another feature that complements your chosen kitchen surfaces. So whilst I love the copper pendants in picture 1.. They could work depending on the rest of your decor and would be a highlight in a neutral white/timber kitchen = Good! If you choose copper you would complement it with a couple of copper bench top items. These are beautiful! (I collect copper because I love it, my kitchen pendants are silver, I renovated to sell in the next 3-5 years) You will see a picture starting to form in your mind and there is nothing wrong with making a statement with your lighting. I found that when I wasn't sure I would get a very strong sense of what was right and what was wrong for a space, then common sense or passion would determine the outcome! Here are another couple that might work, look her on Houzz under lighting, search pendants, then have fun looking!Timber tones with black or white to complement your cabinets... or Statement white pendants for a bit of quirky fun! Your personality can be reflected in your lighting and accessories creating that point of difference from the predictable white on timber look. Plus don't forget the power of greenery to punctuate the theme!

Is your stone veneer to be laid on a slope? I would want to see an example of that beforehand. The stones in a sloped wall are still set horizontally, but the veneer will have joints that look skewed if laid sloped so it could look quite odd.

If you put in black glossy tiles you won't just have to wipe them down once a day - you will have to wipe them down multiple times a day! And I would never put glossy tiles in any colour in an entranceway as yes, they are VERY slippery when wet. We had glossy tiles in a bathroom and would never choose them for floor tiles again.