Currently thunar uses "xfce-filemanager" as icon-name in its preferences dialog. I'd like to point out that this icon never appears anywhere else and therefore I'd suggest to replace it with "thunar" of "filemanager" or whatever is most commonly used within thunar. I agree that this is a tiny glitch, but it's one symlink less in icon-themes (and I stumbled across this because my icon-theme is currently missing this icon :( ). Thanks in advance!
It uses system-file-manager
My bugreport was against 1.3.0, but I see it has been resolved in the meantime. Thanks!