First I would pick a wall finish. I see three right now and it's two too many. Unless you are changing the flooring I would go with a gray / white paint for all the walls. If you keep the vanity I would paint the cupboards over the washer/dryer black, again for cohesion, at a minimum but I would prefer they match the vanity in style too. How is the bathroom used? Is it a main bath, a mudroom bath? What are your needs for this space? A shower curtain would be nice. Do you need hooks/bars for towels?

All walls are same color except wallpaper behind washer/dryer. Shower floor is gonna be fixed. So yes, a shower curtain will be installed after. Looking for storage/decor ideas.

I see a wall color. I see wall paper. I see a faux finish brown surrounding the shower.

Agree with most of above, but does your flooring have more brown than gray as it reads on my screen? Paint color like SW Agreeable gray might accommodate both, and remove and paint wallpaper wall. I would add under cabinet lighting over the W/D. Heavy duty towel hook on either side of the shower. A cabinet with doors and towel bar over the toilet painted or finished like other cabinets. Both cabinets over the W/D and vanity should be the same finish black or wood-tone. A lidded laundry hamper in same tone as the vanity, cabinets, your laundry basket could sit on top. A large fun print on the big blank wall would add interest. When I have traveled in Italy I would take photos of laundry - often hanging on lines strung high above the street. Colorful or interesting, like an old-fashioned corset 😉.

What do you need to store in this bathroom? I imagine the obvious: extra roll of tissue, laundry products.

Does the bathroom get regular use as someone's, or the household's, main bathroom? What kind of use does the shower get? Is it for after swimming? Working outside?

Where is dirty laundry before it gets washed? Do household members keep it in their rooms? Do they do their own, or does one person do everyone's?

Besides laundry supplies, are other cleaning products or tools kept in here? Or does an outside service bring items for cleaning day, and only minimal items like a broom and Swiffer are stored?