Is it possible to set a default cover page image and icon that is unique to a category (but can be overridden)? Especially on events, the creator may not always have an image available, but the event category could easily have a default image set for it so the item doesn't look so generic in the lists. Groups, channels, and organizations could have one too, but those are longer lasting items and a creator would have time to arrange or create an image to post.
Also, what is the ideal ratio for a cover image? Is it possible to have the area rotate through some images or even have a video associated with it like the default splash page? If I build a composite image for the space, what is the safe zone like so any images aren't cropped badly? It looks like the image changes it's ratio depending on the window size/screen size so this may not be practical to consider. Abstracts and patterns might be safest.