This project was neat, but I had a hard time thinking of objects (other than trees) that would look neat with a mirrored effect. However, here are a couple of my designs, and hope that you all check out some of the others on my website.
(the picture below is og a tree. I like how the roots connect again, and this image reminded me of the "tree of life". )
I cropped out part of a butterfly wing, and came up with the pattern below: