Unfortunately all your options require custom work: It looks like you need an 18" corner cabinet. You will have to modify the last wall cabinet on the left. As I am eyeballing it, you should be able to cut the last cabinet in the middle and then shorten the left section to fit the space of the wall next to the door trim. It's an option that makes the area looks symmetric. Or you can install shelves over the sink. I would not recommend it because it will take the looks away. And the last option will be to remove the last cabinet, shorten it so it fits over the sink and install a single cabinet where the double one was. This will leave a triangle space behind the corner where the two cabinets will meet. You can block the space under it. Hope this helps!

Yes they do have similar styles in porcelain, but to me it doesn't look the same. Search around that site and see if any of the other tile designs in other materials strike your fancy. I know you said you don't like the subway, but you could get a glass tile in a 2X8 and lay it in a herringbone or find shorter ones and do a chevron. Don't know if you care for mosaics, or penny rounds, those would also look nice. You are going to have to narrow it down to a look you are drawn to, and then go from there. Search kitchen backsplashes on here to get some ideas as well.

I think wallpaper is not recommended coz the water splashing might spoil its condition. Rather I suggest you to go for a decorative tile panelling up till the width of the loft and placing a backlit round mirror to get a touch of contemporary style with black/white countertop and white and oak vanity.

I have used both with good results. The main difference between Quartz and Granite are 1) price, 2) colour range. Granite generally works out cheaper, because you can buy the exact quantity you require. Quartz comes in large slabs of specific sizes- standard size being roughly 10'-0" x 4'6", so there tends to be more wastage if you don't plan the cutting well. But Quartz is pretty and comes in a wide range of colours and can be re-buffed at a later date. Quartz also comes in various thicknesses- the most commonly used being .75" to about 1.25". And especially when you use dark wood cabinets in a kitchen or bathroom, beige and white counter tops work very well. Some people go even with coloured counter tops like blue, orange, yellow. Natural stone in light colours tend to be porous and stain easily, so I prefer to go with pure black which is safe.