In the days of old, some peoples would perform rain dances to beseech their gods to send them much-needed water. While that's not exactly what you do in Patapon, Sony Computer Entertainment (SCEA) associate producer Chris Hinojosa-Miranda would have you believe in the power of magic to call upon rain - magic background icons, that is.
According to Hinojosa-Miranda, there will come a point in Patapon where you will need the assistance of the rain Juju in order to progress further in the game. It's hidden, though, and you will have to backtrack a bit to the first hunting level in order to find it.
This is where it gets interesting. See the familiar symbols in the picture above? Who knows what you might trigger if you press the corresponding buttons on your PSP...
That one example best sums up Hinojosa-Miranda's point: SCEA put certain kinds of art in the background to serve more than just aesthetic purposes, so don't be afraid to explore and experiment with things in Patapon.