This question was asked on the forums recently which i'll answer with one solution i think is the best: I'm using the Twenty Fourteen
Twenty Fourteen Theme
The tuts in this archive relate to the modification and customization of the Twenty Fourteen default theme for WordPress. Modifications to parent themes should always be done via a child theme or custom functionality plugin.
Add Default Header Image To Twenty Fourteen Child Theme
This code simply pulls an image named header.jpg from your child themes images folder. Copy the PHP code from the view raw link in
Twenty Fourteen Theme: Modify Post Meta Date Time & Author Byline
Unlike StudioPress child themes, there's no post meta filter to help you modify the post info data like author name, time and date in the