The best thing is to use your own pictures in the preview. It gives your file some uniqueness.
probably it is different over the marketplaces, but for VideoHive it’s always better to chose suitable pictures and fill text spaces with appropriate text to make up a nice story and when buyer comes he can see it and think – Oh that’s a nice way how to use this project. this way preview helps to sell the product. If you have lot of images yourself – you can use yours. if not – searching Flickr is an option. don’t forget to check appropriate check box to search for CreativeComons and content to use commercially. and of course save the links to provide them for reviewer when submitting project.
placdarms is an Envato staff member