There's a store on FleaBay where you can find a bunch of cool signs. It's called Jim's Audio Signs and More.
I won't post a link, but I'm sure you can find it via a quick search.
He's got JBL, Denon, Cerwin Vega, Martin Logan, Polk Audio, Definitive Technology, Dynaudio, Carver, Yamaha, KEF, Jamo, Paradigm, Pioneer, Sonance, B&W, Magnepan, Marantz, Bang & Olufsen, Mark Levinson, McIntosh, Bose, harman kardon, JVC, Boston, Infocus, Klipsch, and others.
Plus, there are a few DTS, DTS-ES, and DTS:Neo6 signs as well.
(no Dobly Digital yet)
There are two styles... one is an "engraved" look with black text on an aluminum field, and the other is the opposite - brushed aluminum vinyl lettering on a black field. Very cool!