Johnny Cash had a really cool style of playing the acoustic guitar. He would play with a flat pick and alternate strumming from high up on the neck while holding the guitar down low. He would then strum down low near the bridge of the guitar and just keep alternating between these positions. This was all part of his unique showmanship.
When he did the Sun Studio sessions with the Tennessee Two they were groundbreaking because he had something a little different going on. He would take a card and weave it into the strings, then he would kind of use it as a percussion instrument because they didn’t have a drummer. So with Johnny hitting on his guitar like that, this acted like the snares that would be hitting against the underside of a snare drum. Some people call this style of guitar playing sock guitar.
You can do the same thing without a card, or you can even make some chords, but the focus is on the texture of the pick going across the strings but having that card in there gives it an extra sizzle.
So have a go and see if you can add a little extra rhythm to your playing style.