I've tinkered in the past with customizing Ficcares. My first foray was was antiquing my own Silver Primavara so that the recesses were black. I've since done this for several people, layering primer, black enamel, and finally a clear coat in the recesses of the clip:
Butterfly Lover Ficcare:
These are a lot of fun, but obviously the application of the design is tricky and then there's the many enamel coats. It's very important to do several thin coats to get an even finish. The primary issue with any Ficcare modification is that the clip itself flexes. This is why the teeth soldered to the underside tend to crack at the solder joint so often. That bend of the clip is what flexes the most, and the teeth just don't flex with it. An enamel coating, or any other modification, that can't flex, is going to crack and peel. This is why some of the border collections have colors that will peel right off, the enamel isn't flexing as much as the clip is.
In the past I'd also done a few clips with epoxied gears, and while it held, I still wanted a better method of attaching three dimensional components:
But now I think I've found the best way to add three-dimensional components to a Ficcare, rivets. They're smooth on the back, subtle on the front, and let me do things like this: