You could paint the wall w/more of a satin finish paint. easier to wipe clean.

you could do the upper half w/mirrors,

lower w/a type of wainscot.

Removeable wallpaper/mural

some type of wood slat paneling

these mirror squares are a cool idea

The painted ceiling idea in a cool color is a great idea to amp up the space!

or try something like this

I like this look w/the black ceiling

I like them all!

Why not a fun vinyl wallpaper . I would not do wood and you need mirrors in a gym for sure so do you have those ? Usually when asking about a space it is good to show thw whole space . I sure would not do black ceilings in a gym.

I sure would not do black ceilings in a gym.

why Patricia? The black ceiling looks great w/the wood and black floors. And what's wrong w/the wood panels?

It's a home gym. she can do whatever she wants.