There has been a Harvard study that shows exposure to fresh flowers increases compassion, and decreases anxiety and worry. During the darkest months of Winter, we can reach out the the southern hemisphere for cut flowers such as this gloriosa lily, or fragrant roses. It was found that people were less negative after a few days with flowers in the home, and the benefits extend to the workplace also. So receiving flowers generally makes people feel happy, beyond just the natural reaction to getting a considerate and beautiful gift. The greatest mood boosting effects were felt when the flowers were placed in the common areas of the home. People want to see them first thing in the morning. We know the mind and body register the smallest event, and it's good to know that exposure to flowers predispose to love and compassion. Here is a message from the Dalai Lama on the benefits of cultivating such states. Personally I think they have an effect on general well being, whether or not there is a spiritual component. Reconnecting to nature itself through beauty predisposes us to a state of happiness.
Here is an article that tells more about the study.
The flowers above come from a nice British site with lovely pictures that are pretty uplifting in and of themselves, that gives many ideas for the use of flowers in decorating gifts and for seasonal accents, caring for them in the home, floral trends and ideas.
Smith and Hawken in the U.S. also offers flowers suitable for decorating gift packaging, such as small white amaryllis.