The functionality you asked for is already a built-in feature of Coraline theme.
All you have to do is make sure the image you assign as feature image of that post/page is wide enough ( wider than or equal to the width of header image of this theme ).
If wanted, you can keep changing it by assigning the other image as feature.
I must be blind I don’t see a place to select a featured image. I see where I can choose a custom header and I have uploaded two. Can you tell me where to look for ‘featured image’?
When you edit a post/page look over to the right down below, you would see the box that say set feature image.
If you don’t see that box, look over at the top and click on Screen Options, the options will dropdown, then check to display the Featured images box.
Right in one! Thanks. Now I have to adjust the stylesheet some more. Those questions will in a separate thread.
A further question: I tried to use the twentytwelve theme because it supports a more flexible layout (suitable for tablets and phones) than does coraline. With that theme the featured image only appears in a sidebar, not full width when there is no sidebar.
So I switched back to coraline. Now the featured image simply does not appear anywhere.
Any suggestion what might be wrong?
This site is in the early stages of development. I am learning how to work with WP. Would it make sense to remove the whole thing from the server and start over with a new installation?
Update:
The trick was going back to the Header menu and choosing ‘Restore Original Header Image’.
