One of my favorite looks is when plants intertwine, weaving together different colors and textures. One of the best plants for doing this quite naturally is helichrysum petiolare, (licorice plant). It is a perennial that is grown mainly for its foliage. It does best in sun but can handle some shade and it can spread fairly wide. The photo above is from my front garden in San Juan Capistrano where the bright green colored foliage of the 'lime light' licorice plant extends into a patch of brachyscome (swan river daisies).
This shows the more common blue-gray foliage embracing some annual violas with a little ornamental grass trying to get into the picture. this is from the Flying Rabbit Island flower bed in the back yard in San Juan Capistrano.