What is the easiest way to create a diverse set of cover pages?

word 2016

using the cover page gallery

Explanation:

This is certainly the easiest way. And you just need to add this as first page, set the borders, pagination, headers and footers from second page, and avoiding the first page as it is the cover page as well as customize the various section of the cover page design you choose.

Inserting a blank page will require a lot of effort.

Inserting pictures will not  result into a complete and a meaningful cover page.

Same is the case if you insert shapes.

hope it helps :)