replace the bar with a hand towel ring between the outlet and the mirror.

I'd hang your framed art above the toilet and leave the other wall blank. edit the decor on the sink top.

If you have a shutoff valve on the toilet... get rid of the plunger.

Do you need a rug? a powder room without natural light is drab... painting it a fresh white with an undertone you love would do wonders.

I'd install metal wall decor on the mirror wall and a colorful multiple on the big wall.

You are off to a pleasant start,room has clean lines and no cluttering geegaws.
Mirror is very nice.
You may want to place a large wipeable art piece over the toilet to echo the shape of the mirror.
If there is room on the wall that the toilet faces,you may put some poster art there as well.
A colorful graphic( map or other edifying / instructive design ) will enhance incidental learning when on the throne!
Towel bar seems ok as it is not near the toilet.
If powder room is used by random guests,they may be comforted by seeing a plunger,as they may not have the sang froide to turn off the valve during an emergent problem.

Art for the bathroom should combine style and practicality! I love the idea of using botanical prints, abstract pieces, or calming seascapes to create a peaceful, spa-like atmosphere. For durability, it's also important to choose moisture-resistant pieces or framed art with protective glass to ensure longevity. Whether it's a vibrant floral or a serene ocean scene, the right artwork can transform a bathroom into a relaxing sanctuary.

Sorry to say, I think the wall color and flooring, the dark mirror and perhaps even the lighting’s effect are creating the drab feeling and changing a towel bar and adding art is not really going to help.

If open to painting, it would make a huge difference and then you may feel you want to paint the mirror’s frame lighter. Given the sink is not practical, consider shelves over toilet. Once done, then choose something on wall that pulls the room together.

^ agree, I would change the wall color or wallpaper