To add a main photo for an event as the host: 1  Click Add Event Photo at the top right of the event page. 2  You can choose to upload a new photo or pick a photo from one of your Facebook albums.3  The recommended size for event photos is 1920 by 1080 pixels (16:9 ratio). Click Add Event Photo at the top right of the event page. 2  You can choose to upload a new photo or pick a photo from one of your Facebook albums. 3  The recommended size for event photos is 1920 by 1080 pixels (16:9 ratio).