Any advice on how to finish this project? :-)

Any advice would be greatly appreciated! My ADHD and I started a project stripping the old glass fiber wallpaper from the bedroom walls, but we’ve now run out of motivation 🥲

What’s the easiest (and the most expensive) option from here? Ready-made panels, wall coverings, or sanding + filling? I have a sanding machine and some medium-grade filler.

It's approx. 22 m² in total, and it will either be painted or wallpapered afterwards.