Are we allowed to use stock imagery and stock vectors in templates to sell etc? or does everything have to be created from scratch by the author?
First of all, it depends on the licence . To sell photo included into your project you need to buy an extended one. Sometimes, when you onlu use only some element from photo or you change it you need the regular licence.
It`s all up to file, you wanna use
more about licence here: http://graphicriver.net/licenses/regular_extended