Here's the room with the lights on. Much warmer. Sorry the first photos I forgot to turn on the light!

Have the fabricator who made the sink, make a backsplash to match.

I like your bathroom!

You need something unique. Ai created a mother-of-pearl backsplash that looks nice with your beautiful room.

depending on the length, you could find a ready made marble threshold and router a fancy edge to add for a backsplash.

thresholds come in a variety of whites/creams at most home improvement centers.

I hope you took a sample of the wallpaper and tested being able to clean it.

I just installed a wallpaper in my 'informal' powder room and when I tested their standard paper with a bit of makeup, it started to fall apart when I wiped it with a damp paper towel.

Luckily they also offered a commercial/contract grade finish and some splattered foundation cleaned right up with a damp paper towel. I also wanted the wallpaper to be more sturdy in case my cleaning ladies accidentally got some cleaning product on it near the toilet area.

I don't have any good or helpful solution for you, but just want to say that you are winning the fun and funky bathroom award-so much fun! Good luck, I feel that you will definitely use that imagination to find a great solution!

i love the mother of pearl backsplash. do not use marble. it absorbs everything

Your bathroom is very eclectic so adding one more finish will just be part of the look. Instead of the geen onyk from wet bar (even if available), maybe search for a remnant that works with the paper AND sink’s finish. In the meantime, just get some plexiglass to protect the paper.

If you want to further protect your wallpaper in addition to a backsplash,try painting over it with “dead flat varnish”. It gives you a wipeable surface and doesn’t affect the look of the paper. My wallpapered kitchen backsplash is still going strong after 4 years.