Festive Christmas nail stickers are great Advent Calendar filler ideas, especially for teens or tweens who would love showing off holiday-themed manicures. Cut. Discover advent calendar filler ideas including delicious foodie treats, hair accessories and socks. Looking for advent calendar fillers for adults? Pick from. I can think of many things to put in a Advent calendar for a child but what about a big kid? Like a grownup guy? I cant think of anything inexpensive (under.