Very old yarn/fabric walls need removal/painting

[Max Denning]

Hello, I've got an old apartment building from 1890 in Worcester, Massachusetts. The tenants just moved out and I'm deciding what to do with these walls. They are some sort of yarn or fabric strings that I've never seen before. Looks like they've been on there for quite some time as you can see with the red stains and staining around picture frames (possible smoker?). I'm not really sure what the extent of removing these would be but I've also considered trying to clean them first. I was also told they can be painted on with a roller? Does anyone have any experience with this sort of thing?