Perhaps you could have the concrete walls polished and sealed, like they do with floors?

paint

The only difficulty you'll have is hanging anything on concrete walls. But there are a variety of durable concrete paints available that look really nice.

https://www.etsy.com/shop/katshoa

Hang light fabric panels all the way around and add LED lighting (cool) so that you emphasise the ripples in the fabric.

I'm definitely needing to keep it inexpensive & DIY. I will probably paint some of the walls. I've heard Rustoleum paint is good for such projects. Any of you have experience with painting concrete walls?

In the basement bathroom, the paint is peeling & will require a lot of scraping. Right now I'm not really up to applying that much elbow grease. There are metal pipes running across the ceiling right along the wall that would make hanging light fabric, inexpensive shower curtains a possible solution.

I'll likely scrape the walls gradually, over time. Any ideas on making that job easier? After scraping them, sealing them would probably be wise, unless the paint I use accomplishes that as well.

The basement family room would be cozy with light fabric hanging on the walls. That would trulyy create the atmosphere I want to convey.