I used a sheet of .040 aluminum sanded with 120 grit the long direction to give it the "brushed" aluminum look. Hit it with rattle can clear coat to keep it from getting dull. Kind of a pro street look. Clever
I'm happy with my beige carpet routine (3rd pic from right). http://mmb.maverick.to/showthread.php?t=15524
I mounted my speakers under the steel deck along with my amp. Then I took the original panel and opened up the rough shape of the speaker openings, leaving a couple of 1/2" strips for support. I covered the entire panel in black grille cloth, the stuff that is actually used for speakers. It is very subtle, no speakers popping out of it, and blends with the interior well. Nice texture to it, too. Being black, it does not reflect on the rear window like some light colors do in bright sunlight.