About 8 hours ago an unlisted (not private) video was added to the ENreco playlist on the holoEN YouTube channel depicting a reference NPC prison cell design. While the event itself is months away, perhaps someone here who is interested in submitting a design would appreciate getting a head start. The cell appears to be a cube with an internal volume of 8x8x8 (not counting the walls/floor/ceiling). I'm guessing the containing walls must be stone bricks and one of the walls will have iron bars.

In case the video gets privated, the title was "【#ENreco】ENigmatic Recollection Chapter 3 Build Reference Video" and the description was just a generic ENreco summary. The URL just leads to the ENreco page on the hololive site which still has last year's assets.