The space between the end of the bed and the wall could probably be eliminated, then there would be no convex corners at all in the room.
It could be put all the way in the corner. Or if you kept the bed but made it more of a shelf, it could be hidden beneath the bed.
If it were an opening sunken below the surface of the padding in the middle of the floor, it might represent a trip hazard, while if it weren't sunken, it would be a hard surface to be hurt against.
Well, tripping hazard in a padded room? Not really a problem, your will always fall adequate padded But I planned to have padding above the grate. Center position is easier on the slightly slope one needs to have the water running to the drain and not forming puddles. Have it in a corner would be dificult for the existing construction.
And for the bed, it would offer to much attacking surface if it was like a shelf, and a hiding place that can make an extraction quit difficult and hazardous for the staff. Of course it doesn't look so nicely, but in this case, functionality comes before aesthetics.
No bed at all works. Although a bed with medical restraints would also work (but then why bother with a padded cell).