I'm not sure if this exactly classifies as nature, but wood was originally in trees, and it's a nice pattern anyway, so I've put this up for you to see. This is a stack of planks lying on a wagon (not in the picture). The different sizes of all the ends give the picture variety despite it's repetitive nature. I set this picture as my desktop background, and it actually seems makes my screen look bigger!
Url of this post: http://davids-pics.blogspot.com/2007/02/wood_03.html