Have had this for a while to put an image up on just the Home screen background
/* Add to blank home page online image Gollum - remember to untick Enable Backdrops in Display */
div.scrollFrameY.flex.flex-direction-column.flex-grow.focuscontainer-down.emby-scroller.scrollY.overflowYScroll {background-image: url("https://static0.srcdn.com/wordpress/wp-content/uploads/2019/03/Gollum.jpg");}
div.scrollFrameY.flex.flex-direction-column.flex-grow.focuscontainer-down.emby-scroller.scrollY.ove