Adding colored fabrics like towels, sheets, shower curtains, etc. Large canvas art or fake plants can also add some color and dimension. They are coming out with light bulbs ($60 a pop) that are LED and can be controlled from your iPhone or iPad. These lights can change to any color in the rainbow and can be controlled for brightness.
Most landlords would be happy if you were to paint, but it would be at your cost and the tenant would need to get permission in writing before any changes were made.
Bernstein Realty, Inc.