As I wrote in duplicate bug 1285726, VPN can be used with any physical layer, not just a wired connection. And I don't think it's practical to design icons, for every physical layer, that have a disposable corner just in case a padlock appears in that corner. And even if it was practical, whether you are connected to a VPN or not will often be too important for such a tiny emblem.
For those two reasons, I think it would be better for VPN to be shown with a completely separate icon. On PC at least, a separate icon implies a separate menu, but that's reasonable too -- VPN software on Windows and Mac often does that anyway.
As I wrote in duplicate bug 1285726, VPN can be used with any physical layer, not just a wired connection. And I don't think it's practical to design icons, for every physical layer, that have a disposable corner just in case a padlock appears in that corner. And even if it was practical, whether you are connected to a VPN or not will often be too important for such a tiny emblem.
For those two reasons, I think it would be better for VPN to be shown with a completely separate icon. On PC at least, a separate icon implies a separate menu, but that's reasonable too -- VPN software on Windows and Mac often does that anyway.