Facebook images are perfect for catching the attention of your followers and potential audience and they're more likely to be shared than a text post. It's also easy to create promoted ads from already existing image posts in order to expand your audience.
Facebook images should be a 16:9 aspect ratio. Common dimensions include 1980 x 1080 px, 1640 x 923 px, and 1200 x 675 px. Page header images should be in this ratio as well.