You should use an Image Dimension setting of at least 1200 x 630 pixels for the best display on high resolution devices. At the minimum, you should use an Image Dimension setting of 600 x 315 pixels to display link page posts with larger images. If your image is smaller than 600 x 315 px, it will still display in the link page post, but the size will be much smaller. See Maximizing Distribution for Media Content on Facebook for more information.
Using Wisdom and Knowledge