Experts in collecting and interior design agree that a collector should first study the relationship between the living space and the collection they want to display. Both the individuality of the collection and the ambience of the space must be respected. This involves a delicate balancing act in which neither side is overpowered. Many older homes are rich in architectural detail: mantles, lintels over the doors and windows, ledges, and plate rails - all of which can be turned into an advantage for the collector.
Modern homes, on the other hand, may be stark — without any architectural detailing. While they may lack inherent charm, these walls can serve as highly visible areas where collectibles can be displayed or stored.
In rooms without a fireplace or other dominant architectural focus, a grouping of collectibles can become the focal point. For the maximum dramatic effect, it is advised that the collector allow only one collection or area of emphasis in each room. More than one grouping dilutes the impact and may make the room appear disjointed or cluttered.
(source: http://en.wikipedia.org)