Let's talk about balance
Balance occurs when the main image is at the centre of the picture. Balance is an effect of equilibrium created by two opposing forces.
Balance can occur along the vertical or horizontal axis but is most notable along the vertical axis.
While looking at the pictorial balance we always assume a central vertical axis and expect equal distribution of visual weight.
The simplest type of balance, both to create and recognise, is symmetrical balance. In symmetrical balance similar shapes are repeated in the same positions on either side of the vertical axis.
When you mirror the image you get the same image.
Asymmetrical balance is achieved with dissimilar objects of equal visual weight or attraction to the eye. 
Asymmetrical balance is more intricate and complex.
The third variety of balance is called radial balance. Here all the elements radiate or circle out from a common central point.
The fourth Variety of balance is called crystallographic balance. This is a special refinement of symmetrical balance, in which the same element is constantly repeated all over the surface without equal emphasis over the whole format. This is also known as the 'all over pattern'

This is a summary from Principles of design through photography by  

Full book - https://archive.org/details/principlesofdesi0000math/page/144/mode/2up