First is an image by Vincent van Gogh - La Crau with peach trees in blossom - that I think shows great contrast in several ways. There is contrast of colour with the orange roofs zinging against the blue hills and contrast of value with the white blossoms and clouds against their darker surroundings. There is contrast between the crisp shapes of the houses and the more organic textures and patterns of the rest of the landscape.
There is also relationship created simply by the shapes of van Gogh's brushstrokes - so the blob shapes (good technical term that :-) ) that he's used to create the texture of the sky are repeated in the foreground to create the texture of the land and in the middle ground to create what I think are small areas of water.
The second image I've selected is a medieval scientific instrument called the Chaucer Astrolabe from 1326. I think it is a stunning image with its rhythmic repetition of geometric shapes, the circles, overlaid with with organic images of birds and dogs. Although each of these organic shapes is different, I think there is enough similarity for them to build relationship.
The third image is a quilt by Kevan Lunney. Gosh, where to begin - contrast of value - contrast of shape, circles and rectangles - contrast of size, variation of circle size - contrast of texture, shiny against matte... I want to own this quilt :-).
I've also attached an attempt at stylistic contrast with a repeating pattern using two stylised images of water plus a more naturalistic image of a sea creature, a leafy seadragon which is one of my all-time favourite sea creatures. I'm not at all sure if it's worked so I thought I'd put it out for some comments?