Here's a simple mod I did on a No 06 which has a more practical nature to it than aesthetic, but it addresses something that's kind of bothersome for me about Opinels.
When the blade is closed, the edge rests against the wood of the handle inside the kerf. I've noticed it's a problem at times, when the knife gets jostled, that the blade can slip side-to-side in the kerf and the edge scrapes along the kerf. The only Opinel that I don't see this on is the number 12, and possibly because the blade is so stout.
Here, asside from the handle reshaping, you'll see I've installed a #6-32, 3/16" set screw to act as an adjustable blade stop. I've filed down the blade in that area to act as a makeshift kick, which also serves to keep my fingers a little further away from the sharp edge and make for a little more handle room.