How to change default cover for desktop site and mobile app

For change default cover for desktop site please change your cover you would like to change to cover.jpg and copy overwrite new cover to app/webroot/img/cover.jpg

For change default cover for mobile app please change your cover you would like to change to cover.jpg and copy overwrite new cover to app/webroot/theme/mooApp/img/cover.jpg

After changed file please remember please global cache and your browser cache before testing