Here is a fascinating infographic produced by the people at UK Feather Flags that features lots of information about flags for you to enjoy. The design will teach you about things including the most popular layouts, the most popular flag symbols, the most popular colour combinations and the most often used number of colours. The infographic also imagines what a flag for the planet Earth might look like.
Infographic Source: https://www.uk-featherflags.co.uk/blog/flag-infographic-design/