I've put a number of things up there, including:
- The original PostgreSQL 9.0 Replication shirt
- The PostgreSQL 9.3 shirt
- The PostgreSQL 9.2 poster
- Even a PostgreSQL 9.3 laptop sleeve
Since this is Zazzle, it's really only good for PostgreSQL users in the USA, though. I understand that the Europeans have their own swag store; hopefully one will post a link in the comments.