Comment 6 for bug 292504

It's not libgnomeui's job either; did you click the link? gnome_thumbnailer looks up the mime-type via GConf, finds the thumbnailer responsible for it, and runs it over the file that Nautilus gives it. You install a new thumbnailer by adding the mime-type in GConf and specifying the thumbnailer.

In fact, all of this has already been done (you'll probably want to bump the tools in use to GIO-equivalents, however: http://www.objectnetworks.net/wiki/index.php?title=Exe_icon_for_Gnome)

All that's left is providing a package that does the above for you, which should be done in Wine, with icoutils, or in its own package. It's not GNOME's bug.