Faux rusted metal... That's a great idea, would really give it that industrial end of the world zombie look.
I remember seeing a huge sign at the... I think it was called the spartan mud run.
The sign they had was made of all rusted looking metal and it looked really awesome and matched the mud run theme.
I tend to use wood because it's so easy to work with.
Ive never used Faux rusted metal before, maybe I'll incorporate it in the next project.