It kinda looks like they used a brown paper bag wallpaper technique? I would start at a corner and see how hard it is to peel off, Maybe wet it with a sponge and then try to peel. Depending on the adhesive they used, you might need to use wall paper remover.

Interesting... I’ve never heard of that technique. Thanks for the advice! I will make an attempt to remove it as suggested and hopefully it won’t be too time consuming or painful!

I think it is tissue paper painted on the wall with a pearlescent paint. I would spray the wall with Goo Gone and let it soak in for a couple of hours. Then use something with a wide flat surface to scrape it off.