I got the idea for the Mona Lisa in 2007-2008 while looking at different driftwood images.
The Mona Lisa: Her smile is enigmatic!
The above shot of a close-up of a weathered tree trunk inspired my Mona Lisa. Rather than destroy the underpainting or make it very abstract, I simply painted the outline of the weathered driftwood trunk with little shading over my interpretation of Leonardo's image. I put the steps I took to paint this on my blog: http://www.mattesonart.com/mona-lisa-driftwood-series--a-painting-in-progress-1.aspx this being the first entry.