Yep! We can't even take them down, they're insusceptible to fire, too.

( if he remembers, he believes a few students put sheets over them to bring normalcy back to the dormitory. as for komaeda, he doesn't mind them, and so there's some day he removes the fabric to truly look at them for what they are. there has to be something about them, a hidden secret... )

...I think they're souls trapped. When I use the hacking gun, it tells me that there's a spiritual presence everywhere within the dorm. Almost like the entire thing is a spirit itself unlike the school.