[wulf]

I think the above picture would be less eye-catching if it had three acrobats in very similar poses; it works because the one in the middle breaks the symmetry, creating a tension between that and the connection all three still share.

I think compositions with odd numbers of things are often good but I wonder if the fundamental reason is down to the question of balance vs symmetry. Just having three, five or seven subjects isn't enough - you still need to consider the relationships, which can also be done with two, four or more (eg. countless "madonna and child" pictures down through the ages).

Wulf