Ugly wall mirrors

https://www.hunker.com/13412323/decorative-ideas-to-hide-a-wall-mirror

Paint it with watered down white glue (2 parts glue to 1 part water) then paint it with a latex colour of your choice. the glue will help the paint to adhere to the mirror tiles...not a permanent fix, but should get you by until you want to do a complete redo

Perhaps you could paint them a color that would go with the rest of the walls, you could even stencil something on them once you paint them, since it probably would be iffy if you could hang pictures or shelving on the mirrors without breaking them.

You could cover the whole wall with 1/4" drywall.

you could frost them

Whatever you do....be aware that they are GLASS... and they will still break... painting them will only camouflage the danger.... if you plan on covering them with paneling or drywall.... take the time and take them down

You could fill in the spaces between the vertical wood slats with more wood. You just need to be cautious to nail into the existing wood and not break the mirrors.

You could put 1/4 inch sheet rock up, then tape, plaster and paint. But it would probably be best to remove it all. You may still need to put new sheet rock up, but it will be a much smoother job. Those little diamond mirrors in the middles could cause a problem.

Buy poster board (in your preferred color) and cut to fit into the area. It will likely take several pieces but you can but them up to each other and then use the area as a bulletin board or decorate the poster board in any way you like, maybe even fabric in colors to coordinate with your existing furniture.

Curtians come to mind. Call a few thrift stores to see if there are any present that would be the length you need and the amount.

I would use wallpaper.....

Make simple frames for each section using furring strips - then staple fabric over each one and hang over each section - simple fabric wall panels.

Ooh, I would modernize it a bit by painting over it with a gold or silver in an abstract pattern.. so it looks more deliberate and less "70s" ish.. or try gold leaf also in random abstract patterns...

Is that etching in the mirror. You can google Wall Art. They have peel-able prints. It would be cheaper / easier than removing the mirror

google peel and stick wall art

Of course I have no idea what your personal style is, but these " reclaimed tin ceiling tiles" come on a roll, but can be cut into individual 12 inch tiles that would be gorgeous with cutouts for the diamond shapes in the centers

https://www.amazon.com/NuWallpaper-NU2495-Reclaimed-Wallpaper-Off-White/dp/B07483CT9V/ref=sr_1_1_sspa?ie=UTF8&qid=1520272802&sr=8-1-spons&keywords=faux+wall+panels+peel+and+stick&psc=1#customerReviews