I’m trying to find out if I can get a full width banner on my blog post. At the moment its a full size image but I’m trying to get it to stretch across the whole page
Please see attached screenshot to get a better idea
You can set “Large image” in the Theme Settings > Blog > Single post design and set header overlap type for Single post header. You will get the result like this http://prntscr.com/o5m3cc
There is no other option to make the image full width.