Well actually its just an overlay border on top of your desktop. See 'CRT Screen' project.
You can add a transparent border to your desktop, making it look either like
- a crt screen (ie glass like bevel)
- an old apple UI (rounded corners)
- an old terminal with some buttons. (Works nicely in combination with cool-retro-term, though the cool-retro-term window has to be exactly on the right position, directly under the crt window)
Needs tweaking to work.
(xfce theme is the 'CDE theme')