Going with the AT theme, I am thinking delectible mountains for a border. First, I pulled fabrics from my closet and arranged them light to dark. Then I had to play with the sizes. Arrggh. It only took a couple of tries to get it close. I made a scrap one and now i have to make the real ones and then add them together before i know if it works. I can always add or subtract plain borders to get it the workable size. 
So, how are you all doing with your centers? Let me know if you would like to see my book on the mariner's compass.