Really pretty design!
Consider brass or antique brass hardware.

First stop going ti HD to get design advice the sales people can only do what the software allows . Get a n independant Kitch/ bathoorm designer to design first then go shopping

Those all look very generic in style what is your style in the bedroom ? IMO master BRs and baths need to work together style wise .I think spa and timeless can be done but I need more info from you . First how big is the bathroom? Do you need a tub? Waht colors and woods are in the MBR These spaces are not designed apart . I do not like wood look tile on a shower wall and for sure not ribbed ever. I hesitate to go kitchen cabinet look in a spa.

That is really blandly generic, so yeah, it probably won't go out of style. I don't think gray goes with beige. The beige shower tile and gray marble isn't a great combo. Black faucets are a trend that will probably die at some point. I would really hope bland beige and gray do, too.

No one has a crystal ball as to what will be "timeless" for the next decade or two. Some of your choices will most likely not be considered timeless: wood look tile in a bathroom, black plumbing fixtures, pebble shower floor (have you stood on those in bare feet?), and accent walls of any kind (painted, wallpapered, wood trimmed, or tiled). Shower walls with texture won't be easy to clean and neither will the pebble floor and black hardware. What is the flooring that will abutt the bathrooms? If you're putting wood look tile in the baths, will they be next to real hardwood flooring since that will not be a good look.

Very much agree with Patricia about the independent bath designer vs big box store salesperson when you gut-renovating two full bathrooms.

First.......

Where are the existing bath you are doing? Pictures?

What is the layout? There are no less than eighty million images one can find, that feel clean, modern and suggest a spa.

Your Home depot is looking rather yawn....

First?

Show what you have. what does the Primary bedroom look and feel like? The hall bath is what, as of now?

You don't have enough context to advise: ) Other than pebbles in the shower are a bit "come and already gone". a fad......

does this style complement your home? while nothing is timeless, I think having a bath suit the home goes a long way -

agree to skip the pebble look flooring (but just my opinion) I would also skip those long open shelves - they are hard to keep clean and will get cluttered either with personal products or unnecessary decor items

My issue is this and I have mentioned it befroe. You are in construction now and picking pieces and finishes bit by bit. You need to slow down and select everything before going further or you will end up with nothing going together, just a bunch of random finishes with no cohesiveness.

For me a "spa-like" design usually means a bath of larger size that has space to include amenities of a spa - soaking tub, separate shower or a wet room that combines a shower and tub. A steam shower would be nice to include in a spa bath. Would include plenty of storage and would incorporate plants as well. A skylight would also be a nice addition as introducing natural sunlight would be luxe!

I don't know if it's possible for anything to not be "outdated" in ten years, although most of us have no intention of remodeling our bathrooms and kitchens every ten years. The look you're showing is what is "in" now so I think it's doubtful that it won't say "2025" in 5-10 years. Do you like it is the only thing that matters. Of course you also want it to be well done and some of the commenters have already given you some advice on that, but again, do you like it?

Five years ago we bought a 25 year old house. The secondary bath is all white. White floor, white vanity with white countertop. While I never would have chosen to do that, I had to admit that it is pretty timeless. We replaced the faucets and light fixtures and painted and it is perfectly fine. Not the peak of style, but not unattractive. The tub has a shower curtain instead of a glass door, so it can be changed whenever the urge strikes and white goes with a lot of different colors. We did remodel the primary bath as it had some undesirable features. I suppose it's already outdated by some measures after only four years, but I still like it, so I don't care.

This is not to tell you to do something all white, but to suggest you either do something you really like or something that is pretty plain that will accept revisions over time.

Those look good and very spa like. It needs plants, some zen art, and natural accessories in handmade pieces like carved wood and clay pots.

@Patricia Colwell ConsultingMy style is the style that would appeal to most people! Thanks!

Wood-look tile and pebble-look flooring have already been dated for years, and tbh I don’t think those features would appeal to most people, although admittedly I am not a pro. In my experience pebble-look tile is uncomfortable to stand on and hard to keep clean. Please do consider hiring a professional to help edit your ideas and help you achieve a cohesive “spa-like and timeless” look as you say is your goal. You seem like a very kind person, and I hope your project is successful.

I did not see the pebbles but no, no pebbles or wood look tile.

Timeless is white marble shower, white marble wall tile, white marble countertop, white painted walls. Mid-tone wood vanity. Chrome plumbing fixtures.

For the floors, a solid pale gray or solid pale tan for the floors and match the shower floors but in mosaic.

Your black (or other color) can be introduced in accessories, picture frames, window coverings, curtain etc.

I basically described our bath remodel and if feels very spa-like, open, and timeless.

To everyone who suggested to get professional help. I think we are getting professional help. Please do not underestimate the Home Depot design consultant, as he just graduated from design college and he had experience working for MSI and has a lot of kitchen/bath design experiences. We really enjoy working with him (and brainstorming with everyone here).

@tracefloyd: I agree with you that timeless is white marble shower. So for now, we have tentatively decided to go with "Eden Calacatta" (for both hex floor tiles and wall tiles) and "San Marino Gold" (matte, non slippery) porcelain tile for the floor (see photo):

We believe the subtle gold tone should match well with the 30" oak floating vanity really well, and should be timeless. Any thoughts? Thanks again!

I agree with mcarroll16, “Not marble-look quartz with heavy veining. The uber-dramatic quartzes will look dated soon.” The bold, dramatic veining and gold color is very busy, and certainly not timeless. To me, a “spa look” means relaxing and calming, not overly stimulating with gold veins going every which way. Perhaps you can buy a box of these wall tiles, lay them all out on your floor to get an idea of how it will look, and see if you are pleased before you proceed- you can return them if you decide they don’t work. If you like them- it’s your house! I think white marble (minimal or no veining) would be lovely. I do like hex tiles (in general) on a bathroom floor.

The hex tile looks busier than I would have thought on the site - agree to buy a few boxes and lay them out - I also would either do flooring or shower tiles with (subtle) veins but not both -

if you want timeless: nothing ages better than simplicity