Can you post a drawing of the bathroom layout? 9x5 sounds big for a powder room - I'd think you should have plenty of space for storage. My master bath (with alcove tub/shower combo) is 11x5.

That does sound large for a powder room. Love the sink. You should have a place for a small cabinet with those dimensions, either wall mounted or on the floor. Preferably with doors. Needs in a powder room aren't space hogs, but I like a minimum of cleaning supplies in mine (something for mirror, sink, toilet), additional TP, a few sundry things that a guest might want and wouldn't have to ask for. (dental floss, tylenol, an antacid ;0), bandaid). Waste basket.

If you have the right space for a decorative and functional cabinet to sit on the floor, out of the way, then you should be okay. Personally, I would always use an enclosed vanity where you have the space, and leave the decorative details to the lighting and artwork. You might also be able to use a recessed niche with a door that would be deep enough for toilet paper.

Thanks Ladies. This is the drawing of the layout.

Depending on the layout, there are options for the size of the sink and metal accessories, though a supply cabinet seems like a good choices.

What size sink/vanity do you need. There are great looking vanities which will allow you storage and a similar look. This one seems to fit the vibe you're going for. It comes in different sizes and you have a choice of tops. https://www.fairmontdesigns.com/bath/charlottesville-wbrass-30-vanity-polar-white/This one has a shelf so you could store some toilet paper in a basket. https://empire-industries.com/product/westhampton/

I can't stop thinking that the vanity should be against that wall at the bottom of your drawing... that it was *meant* to be there...

any way you can inset some shelves between the studs and have a door?

or have some pretty open shelving? it's easy enough to build

Along the lines of the comment above mine, I was going to suggest that, if you are using paneled wainscotting, that you put recessed shelves behind one or two of the wainscotting panels across from the toilet and have hidden hinges and a pop-out-when-you-push-in system for opening the wainscotting to reveal hidden storage. It can be recessed into the wall cavity if you do not have room to bump out the wall in the next room. That will hold regular rolls of TP, bottles of cleaner, the brush for the toilet (hang it on a hook and put a plastic tray under to catch drips), and stacks of folded washcloths and hand towels. Be sure to have the other wainscotting panels milled just a bit thicker to match up to the extra depth that the hidden doors hang.