If you can graphically reproduce a sign and if it adds more distinct characteristic to your good/service, then you may register your mark. Marks that are allowed by law to be registered: 

• Words,
• Slogans,
• Names,
• Colors,
• Sounds
• Smells,
• Shapes (three dimensions),
• Devices,
• Trade dress,
• Collective marks,
• Holograms