How much storage do you need? Is this the main bath?

This is the one and only bath. Need more storage for beauty products, hot tools, extra towels..

It doesn't appear that there is space for a cabinet except above the toilet. Not fond of those. Instead, I would first add pull-out shelving in the vanity to maximize storage - that should give you lots more space. If it isn't enough, store daily "stuff" in a caddy in a close-by hallway/room and move it back/forth for use. Extra towels can be stored in a different closet and brought in when needed, or store them in a large basket near the corner of the tub - this one is from Pottery Barn

If your bathroom is really 5 foot and 11 inches, maybe you could fing a shallow wall or tall cabinet to put across from the vanity.

If you go custom, you could recess the storage.

Ikea offers some bath storage.

Can you change the vanity to be 30? that could give you at least that much more room in the med cab and the vanity. Also - Anthropologie has some delightful solutions (not sure if this is your style tho) for storage - great shelves, hooks, or even a ladder for towels?

It looks to me like you have room for about 30 inches of cabinet space across from the vanity. I would mount two 15 inch wide 12inch deep wall cabinets on that wall with the tops at counter height, add a counter top also just 12 inches deep - add two additional recessed medicine cabinets one above each cabinet. That will give you a fair amount of extra storage.

Could you mass some plain mirror medicine cabinets or IKEA shoe cabinets on the wall opposite the toilet? They wouldn’t be deep, but they would hold a lot of little things. Or have a recessed shampoo niche in the wall of the bath tub if it won’t destroy the tile? A small ottoman might fit in somewhere and provide storage. If children are involved, there are tiny footstools with storage that could serve two purposes. Also, shower curtains with pockets, but I suspect they would always look messy and eventually tear out, anyway.

Look at a wider sink cabinet with a smaller sink: more counter space and more interior storage. There are interior storage racks available in many sizes.

a medicine cabinet above the toilet will be helpful. you don't need to store extra towels in that room. I lived with many tiny bathrooms. only the "every day" things were stored in there, plus one spare TP roll. all "extras" were stored in a different closet down the hall.

find creative storage ideas, such as hanging some of your most-used hot tools off the side of the vanity, or organizers that attach to the inside of your cabinet doors.

this one is really nice, I found it on etsy:

utilize the fake "drawer" under the sink:

door racks -- check places like The Container Store or Amazon for things like this. here's a link to a bunch of different ideas.

the Container Store has tons of different sized stackable bins and drawers.

The end wall next to toilet you might put a couple shelves there that you can use cute storage baskets on.

I am going to assume that the wall the sink is on is not an outer wall, given the plumbing there. That means that you can recess a medicine cabinet there. If the vanity area is backed by a closet on the other side of the wall, you also have the option to put a deeper medicine cabinet there. If you can afford the high prices, they are available up to about 8” deep. Or you could put in a recessed cab that protrudes an inch or two beyond the wall and is deeper than what you have. A fully recessed cabinet will make the vanity space feel more spacious.

You need to keep 16” or so from the centerline of the toilet going in either direction clear of other fixtures. You can look for a larger vanity that uses some of any extra space there. These days, you can find vanities in odd sizes, not just 24” or 30”. Do searches on qualitybath.com or build.come and Houzz and you will find them. It looks like yours might be 18” deep, and you will want to keep to that.

If you can, put in an in-wall pocket door for this room. Your pocket door will tuck into the wall next to the toilet. There is probably a light switch to the left of the current door. For a pocket door, you will have to move that to the right wall. What you gain by doing this is to have the entire wall on the right side wall left to use for storage. You have all the space between the studs available to you. If there happens to be a closet on the other side of that wall, you might even steal a couple extra inches there. Although you could use the recess space and add a few inches inside the bathroom to create deeper storage, you have to be careful to not cramp your space for dressing in the bathroom.

I have a new closet opposite my vanity. The shower I put in to replace my tub/shower is about 8” deeper than the tub had been. At the end of my tub, in the next bedroom, there is a closet. Since the wall was moving out 8” it meant that the closet was getting 8” deeper, too. So, on the bathroom side of the wall, behind the closet, I had my builder put in a cabinet. It is about 11” deep and gives me excellent storage.

If you have the ability to bump out into the adjacent room or closet, you can put in a little closet like mine. It easily holds TP, bottles of toiletries, and even folded hand towels. We keep our clean bath towels on top of our train racks, one of which you see above my new closet. My wet towels hang here. We have a second train rack above the toilet for my husband’s wet and clean towel storage. Our room is a bit more spacious than yours, and these train racks do give a bit of a closed-in feel, so I am not sure if you would want them.

This photo cuts out the first 3.5 feet of the bathroom.

You could use the spaces between your studs in the wall oposite your vanity and toilet for storage of all kinds of toiletries. If you can make the storage 6” deep or so, you can store toilet paper there, and you can imagine how much space you would need for a big package of that. Washcloths and maybe hand towels might fit, too.

My idea for lining the inside of the wall cavity after you remove the drywall is to line the cavity with thin metal in order to use as much of that space as possible. Maybe you can take the dimensions to a ductwork sheet metal fabrication shop to have the interior lining made. Construction adhesive can hold it in place. If you decide to have your storage deeper by protruding into the room a few inches, a wooden frame can be made that will hold the door (which you can order online at Barkerdoor.com or other custom door manufacurers) and attach to the studs. Just have the sheet metal shop include that extra depth in the liner they make.

Make these in-wall cabinets as high as you like. If you are comfortable making a header, you can make a cabinet span two stud bays. Otherwise, you can put the cabinets in adjoining stud bays. Or just make one tall cabinet.

One last suggestion I have is also from my own experience. I love the storage in my half bath vanity, which is this style.

Dior 28" Single Bathroom Vanity Set White, Ceramic Top · More Info

The two drawers hold anything you might need at the toilet. The door space is very accessible and stays neater than the bottom of a doors-only vanity. This one is 28” wide and 18” deep. Houzz also has one 26” wide, as well as plenty of 24” and 30“ ones. Other online sites have these, too.

Best of luck with your project. I hope I have helped you think outside the box to creative kinds of storage.