A really simple way to add some interest to your layouts or cards, is to layer cut out pieces of pattern paper right on top of the exact same pattern paper. Because you have the same patterns on top of each other, it's a nice subtle touch, that still adds a nice, clean visual interest.
Step 1 - Cut a piece of white cardstock to 7.5" x 9", and fold in half the long way. Cut 3 pieces of pattern paper, to 3.75" x 3". I used Bella's One Fall Day papers (Just Leafy, Needle In A Haystack and Country Fields). Adhere pattern paper to front of card base, and round the top and bottom corners.
Here's another take on the same idea.