FreeCAD plugin for tumbler
Tumbler is a rather new thumbnailing system developed by the people at xfce. It is used by thunar and marlinn file managers. I just made a plugin for tumbler that allows it to display thumbnails for FreeCAD files (provided you enabled thumbnails in the FreeCAD preferences).
Get the code here: https://github.com/yorikvanhavre/tumbler-fcstd-thumbnailer.
I plan to include this in the FreeCAD sources or the tumbler sources, depending if the xfce devs find it useful