Fallout: New Vegas locations project
Upon first entering the entrance several speakers are active, some of which are shielded, and will not be turned off until the Casino floor has been visited and completed. The Receptionist's terminal found on the welcome desk can activate/deactivate holograms once you locate the security code found on The Tampico's front desk terminal.
After progressing far enough with quests, ghost people will begin inhabiting the room since they've found a new way in besides the front door.
After coming back to the lobby during the course of the game, you will hear banging coming from the entryway, which is purportedly ghost people trying to get inside.