Have you searched through the picture on Houzz? I've found a lot of ideas there.

Go to the better tile showrooms in your area; they will have plenty of options and sizes for your project. Once you start liking a tile line, it's easy enough to pull the rest of the elements together; but you need to see what's appealing to you in person.

I like the quartz with your theme. It's like a gravel version of the pebble tile. You get the gray without the heaviness of a solid gray quartz like in your first choices. But I sure wouldn't use that pebble tile as a vanity backsplash. There is enough going on with the heavy grain of hickory, the speckled quartz, the faucet, mirror and light. Adding pebbles everywhere becomes too thematic. Just use the quartz as a backsplash. Add interest with the mirror and light if you think it needs more around the vanity. My cabinet maker has a display for dark stained hickory. They did slab for the shallow drawers to let the beautiful grain show. I recommend slab drawers for grained woods like cherry, hickory, and walnut. I like the dark stain because it eliminates some of the stripeyness of hickory that you can see in your sample, as do the slab drawers vs. a pieced drawer. These cabinets appeared a little darker in person so I think it's a darker stain than what you selected. The cabinets are inset. Aren't they beautiful?

I think you're going to want to take your color cues from the finishes you choose for flooring, cabinets, etc., especially in the bathroom. Once you have those, start pulling paint swatches that coordinate and take you in the direction you want to go. I've seen some lovely and classic looking barn doors done, so I'm sure you can pull off the look. I have seen people caution against using them between bedroom and bath though, as you may have more light and noise leakage that you get with a traditional door.