It’s fairly empty, not that many personal touches. He’s never been to the Batcave yet, not yet. But when he does show up, Dean’s sure he’ll want to fill it up just like Dean did with his own room.
So Dean makes sure that he’s got a proper bed, that the bedding is freshly washed and there’s plenty of storage. A dresser that’s got a few clothes that are too small for Dean. Sam insists on installing a bookshelf and once they finish it, he places a few books there, tells Dean that they’re ones he found in the Men of Letters collection that he thought Cas might like.
The room is sparse, but it’s warm and cozy. Dean’s chest aches, but he digs through his journal until he finds one scrap of paper, the edges worn and creased. He smooths it out before he sets it down on the bedside table. He thinks maybe he should say something, and the words on his tongue (“Please come home. Please be okay.”), but he doesn’t say them. Just takes a deep breath, smiles because he has to and turns away. He shuts the door carefully, softly.