'Retro-decorating' is a concept borrowed from the care of dementia patients. Trials in Liverpool found to have be very good for helping dementia sufferers who had become withdrawn (http://www.bbc.co.uk/news/uk-england-lancashire-15111407). The simple placement of furnishing or decorations can trigger memory in a person with dementia, allowing them easier access to their memories.
This concept can be applied to elderly people, or possibly even people with depression. It is taking the idea of photographs to preserve memories, and extending it to the entire environment. The decor will be suited to the individual, to encourage memories and comfort from a positive time in their lives.
My Grandma moved into an elderly home a couple years ago. It was tough on her, she really didn't want to move, but we knew if we didn't force her to move out of her three floor condo she wouldn't be around for much longer. She was resistant to the change and the added stubbornness of a proud older women didn't make the process very easy. What helped her settle in was moving her old furniture into the apartment. When I walked in, I felt like I was back at Grandma's house - even the set up felt felt familiar. I think this small bit of consistency and familiarity helped her to adapt to change and certainly makes her more comfortable.