Themes to make being root scary
Opening applications with sudo is becoming more common and many quite inexperienced users are finding instructions to do so on forums, etc.
It should be clear to a user when opening something like a filebrowser as root that they are able to do damage to their system and that it is not the 'normal' way to do things.
In XFCE, Thunar and Mousepad do a nice trick of having a red box when you're running the app as superuser to warn you that bad things could happen.
It would be ideal if there was a way to implement this in a non-application-specific way.
Using different GTK themes with the same name
One way to solve this problem is to create or choose a red icon and gtk theme, place those in the .icons and .themes directory in /root, and then make that theme have the same name as the icon and gtk themes being used by the user - obviously when a user changes their theme this will be lost, but many people don't change their theme (arguable those who do don't need such cues) and there might be a way to adapt it to make it more flexible...
The above solution is probably unacceptable because /root, like user home directories, is not a valid install directory.
Here is a screenshot to demonstrate what I'm talking about... Nothing says 'beware' like red folder icons, right? In that screenshot you can also see the way a red bar is used in Thunar.