The Image Block allows you to display a specific image to the user. This is useful if you would like to add visuals to the page to style the App, or to present important information to the user in a way that will stand out and attract attention - guiding your visitor's line of sight.
Strike a balance between style and performance. Keep in mind that the larger the file size and the more images added to a single App Page, the longer the loading time. This effect will be felt during both design (open and save of an App) and run time.
When in doubt, use fewer images and aim for a file size of 200kb or less.