Chunks of meta data got moved around in my testing process and what I have come up with is, Facebook does not automatically decide on the best image for share links. After trying a couple of tests, I found that Facebook will take the first open graph image that is defined. Other versions of the image can be selected by using a navigation on the Facebook Link Preview. This appears as a forward and backward button at the top left of the image.
To address the Facebook default to first defined image, I moved the standard link share image to the top of the list. The resolution of this image is 1.91x1 or 1200x630. So make sure you are defining this open graph image first!