Aspect Ratio of Images
Aspect Ratio is incredibly important when uploading images in the generic template (such as the card and list component).
Facebook recommends a 1.91:1 aspect ratio for images in the generic template.
So what does that mean for you?
An aspect ratio describes the relationship of an object’s width to its height.
Since Facebook recommends 1.91:1 for images in the generic template, it is important to make sure that images are around this aspect ratio otherwise the image may be scaled or cropped. If you have a photo that isn’t near this aspect ratio, either use your favorite photo editor to edit your image to fit this aspect ratio or use a different photo altogether that has an aspect ratio near 1.91:1.
For images in an individual card in the list component, an aspect ratio of 1:1 (square) is recommended:
Here are Facebook’s recommended best practices for using the generic template: