I keep it cohesive with using a couple of colors as the main theme and build. (theinspiredroom.net)
I purchases all of the flower pots at the dollar store and gave them a quick coat of white spray paint which gave them a cohesive look. (tarynwhiteaker.com)
We've only tackled a few spaces in our house and I could use help making it cohesive but not boring. (theinspiredroom.net)