The North American rule of thumb for decorating is to display items such as vases or photo frames in odd numbers. On my recent trip to the Netherlands, I found that the decorating style there is to display items in even numbers. And it works!
Why? Well a symmetrical display of two identical items is a balanced look that is pleasant to the eye.
If there are more than two items and they are different colours and sizes of the same shape, a small cluster can be a more interesting focal point. For example, an artist might use three focal points in a painting because it creates more interest instead of having just one or two focal points. The irregular visual causes the viewer to look longer as they try to find the main focal point. People are naturally drawn to visually balanced displays, so when artists and decorators add a twist by creating balance in an odd numbered collection, it is sure to get the viewer’s attention.
In many ways the variety of shapes and heights in a collection is more important than the number of objects in it. I think the photo below of a window from a home in Kinderdijk, Netherlands shows this example beautifully.
Everything is balanced using the rule of reflection symmetry.
So what is your preference? Do you like the pleasant balance of displays with an even number of items? Or do you prefer the dramatic effect of offset, odd number items?