In my journey, I took to looking at the skin of produce through the foldscope. I looked at grape skin, blueberry skin, jicama, and apple skin. Grape and Blueberry offered interesting results, but apple and jicama were too think to allow light through, meaning the image was completely dark.

Grape:
The grape skin has these interesting lines running through it, likely some kind of vein.

Blueberry:
The blueberry has an interesting texture pattern throughout its skin; it is bumpy, with sporadic dark spots.