Leather filigree or cutwork is something I've never done before but after our trip to the UK this fall I'm thinking about doing it as my next type of leatherwork I want to explore. It will fit well as a way to decorate many of the types of items I've already been learning to make.
Basically, the idea is to cut out pieces of leather from your item so that you can see the underlying material. Often, the cutwork leather will be layered with a coloured piece of paper or fabric, so that the nicer colour will show through (often a colour that you couldn't produce on the leather itself). In the case of shoes, the cut-outs would reveal the colour of the hose being worn underneath.
There are lots of artifacts with cutwork or filigree. You often see it on shoes, jerkins etc. However, the most impressive I've seen was from the really cool Islamic leatherbound books at the Chester Beattie Library, which is what's really inspired me for this research. The level of detail was incredible (we're talking extremely complex patterns cut-out so that there was only milimeters of leather left between the shapes). I have no idea how they did it (but why not learn). Of course, something tells me its also going to lead me down the bookbinding path as well. :)
So as a starting point, I thought I'd gather some period examples of leather filigree here, along with links to useful information and more modern how-tos.
Period Examples & Documentation
Online article on the use of filigree in book covers from the 15th & 16th century: http://islamic-arts.org/2011/filigree-bindings-of-the-mamluk-period/
Article on the bookbinding of the Ottoman Empire: http://www.home.umk.pl/~tsb/sites/default/files/numer9/rukanci.pdf
The Chester Beattie Library Guidebook (which we bought on our trip): http://www.cbl.ie/Shop/Guidebook-to-CBL.aspx
Pinterest board of filigree/cutwork artefacts: http://www.pinterest.com/DafyddapAlan/leather-filigreecutwork
Modern How-Tos and References
Discussion on Leatherworker.net about how to do filigree: http://leatherworker.net/forum/index.php?showtopic=33670