This image is 1600px X 800px (2:1 aspect ratio). This image will not take up most of the page as the head image, however, it may not be proportional to other images on the page like this one.
On the bright side, you can make captions.
Unfortunately, the main article image can not function as a "in line with text image" like in Microsoft Word. It must take up a given amount of space at the top of the page with out any article body text next to it. However, it could be possible to put an intro to the article next to the article image, and use that intro in the newsfeed to draw people to the article because there is no article body text in the newsfeed right now.
Just some ideas...
