OpenRaster files are ZIP archives, and has a PNG thumbnail stored at Thumbnails/thumbnail.png (just like OpenDocument Format). There is some code I believe to be a working kio slave implementing this at: http://gitorious.org/oratools/oratools/trees/master/thumbnailer-kde Please evaluate if this is so and advise on how to get this functionality included. Full specs available at: http://create.freedesktop.org/w/index.php?title=OpenRaster/
Created attachment 39395 [details] Example OpenRaster file
Boudewijn, see bug 290528 comment #5.
Yup, that fixes this. *** This bug has been marked as a duplicate of bug 290528 ***