How about a nice TP holder and a piece of art above the toilet . Not every empty space needs to be filled but TP storage IMO should be close to the tollet.I ahve one that is just a stainless tall can with lid . really smple . Not sure about your style but google TP holders and thre are 100s

What does the other side look like?

I would put light, open floor shelving with room for spare hand towels, a scented candle, etc. And I think wall paper might be great in this room.

Do you need storage? I might consider a small cabinet for toiletries and maybe even a small waist can. If you already have a place for that stuff I may not put anything there as mentioned above.

storage cabinet with room for everything one might want to have at hand for toilet-related needs -- plunger, extra tp, pump-liquid hand soap, paper towels, whatever. I would get a cabinet with door pull on right side.

Wastebasket between cabinet and toilet.

I like plants in bathrooms if they get some natural light.

A nice antique or vintage small chest of drawers or cabinet.

You can build or purchase cabinets and shelves for this area.

Do you have a sink across from the toilet? If not, I'd definitely bring in a small pedestal sink. Every toilet should have a sink next to it.

I also like the idea of bringing in storage. You'll need it for toilet paper now, and -- as you age -- you may find yourself in need of various items near the toilet. My grandparents both did, and now my stepfather does.

Obviously, you also need a nice floor mat and some artwork.

Mural wallpaper! There are so many great ones that really tranform the feel of a room.

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Is this a toilet room or a powder room?

You can certainly wallpaper that back wall or all the walls.

Lots of great wallpapers available these days. Every imaginable design and color.

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Looks nice

Nice wallpaper! Put it in the toilet area, too. If it still looks “weird” I would find a cute cabinet to fill the space.

You do need a wastebasket somewhere in there.

Nice bathroom. Black faucets will work beautifully. Buy black towel bars too.

Your bathroom, not mine. But honestly, I like the stainless/silver rather than the black. Reminds me of the poster on this website who wanted to paint her house gutters black.

Practically speaking, it is nice to have spare rolls of toilet paper close by to those using the facilities. So a waste basket as well as some sort of container (cabinet/basket/etc) for bathroom necessities could fill up that space.

Why is there a towel bar in the toilet room? Is there one in the tub room?

You will have a good laugh at this but I also just moved into a new house, and when approaching the toilets there was nowhere to put my phone!! I would at least put a little table next to the toilet, with essentials on it or tucked under it.

I like the idea of shelving over the toilet... for cell phone (☺️)... Or other things you might need there. I like other ideas too and will just add one for you to consider, which is just a tall potted plant, perhaps of a kind featured in your wallpaper. 

But for an actual opinion: I think in your bathroom you might be able to use some storage in that empty space though. These tall narrow dressers may have a name but I don't know it. They come in all sorts of finishes. This one is white, but you should get one that coordinates with the adjacent room and the rest of the bathroom. Wood, painted, mirrored, cane, contemporary, traditional, farmhouse. You could get a painted one and add stenciling if you want. All sorts of possibilities. I don't know your style preferences. With your wallpaper, maybe a cane one would work.

I also vote for the same wallpaper used in this area. I caution you to replace with all black metal. Think of carefully mixing. Your shower components should not look like a complete disconnect. So, for balance, consider keeping mirrors black and then doing black hardware on the cabinet. But leave the faucet and light. I find all black fixtures and metals too jarring and visually jumpy - unless it’s a moody vibe and all the finishes are dark and then they just blend. You have a very bright white environment and the wallpaper is going to make a big impact. The space won’t want more black. A white cabinet next to the toilet would be perfect - I’m not a fan of open shelves over toilets. Ewww

Side note - that TP holder seems far out of reach and if so I’d move it closer to where it’s needed or maybe it will work on the cabinet you get - if you go that direction.

A powder room such as yours would be a fantastic place to go a little crazy with design. So, yes to the wall paper, to additional storage, dramatic lighting fixtures, etc.

If there is a vanity with usable under -sink space, the toilet paper doesn’t have to be next to the toilet. I would be concerned about overcrowding the room because of the empty area.

Hence, the suggestion that a fully wallpapered room will be a great way to make it about THAT design feature - and not this one annoyance. The photo posted by Norwood is a divine example of how paper takes the attention immediately.

Yes - I agree with all comments above! Will definitely wallpaper the toilet room also and I do like some of the storage cabinets shown in these examples. I agree that some form of storage would be ideal and am leaning towards the cabinets vs open shelves now.

Maybe this was built for someone who used a walker or a wheelchair. That space was there so they could turn around. The towel bar may be also a grab bar. If you don't need the extra space (I would love it!) you probably do need some sort of storage cabinet for toilet paper, extra soap, towels, and maybe cleaning supplies. Art on the walls would be nice.

you have so many ideas already but since you are bringing black into the room and wallpaper I found so many cool ones for another project searching black wallpaper on Etsy. Searching black wallpaper on Houzz comes up with completely different options. I used black crane wallpaper before and it was striking. https://www.etsy.com/search?q=black%20wallpaper&ref=search_bar

agree with using it for storage