If you want to add them I think it may be an interesting idea to put the Full HD art as picture in frames around the game or maybe as collectables you can add to a picture book. It is a good easter egg and it can add something else for the players to do around the maps.
Viewing post in ( NSFW ) HD art or Pixel art? comments
^^agree
the pause menu is referred to as your "Book of Life" that records all your events in this life and adding a memories section to it would be very fun. like have all the slots empty with little hints at what leads to them
"Forgot to knock", "Midnight Snack", "Rainbow Factory"
if you know you know :))