Bit confused by your choice.  Setting permissions to - let's say - admin or moderation would allow site operators to select featured images.  This would be used to add status to certain images and individuals.  In theory - and practice - that has significant social and cultural value (status as a cultural meme).  Can be very useful for individual with low esteem and a great way for - let's say a teacher - to help a student.  

How much - cost to me - to have you implement a favorite block showcase and showcase view that can be assigned to albums in spaces - (groups and orgs would be nice to keep the interface consistent) and would show up on the home page.  If favorites for albums in a given space could show up in just those space - that would also be nice, but I am not certain how the block would be labeled - it would be essentially the same as that for a public album.