I like the age-old motif of hearts and keys. It never goes out of style and always seems so genuine and proper. I also like gags involving swallowing a key like in "Arrested Development" so with these cupcakes I'm all set.
You've got it right there, egg salad and crisp lettuce are indeed the key to my sandwich happiness. Bonus points for a little horseradish mixed in and a slice of provolone. I've got a drool cleanup on aisle keyboard!