Personally, I'm a little conservative that way. I think a simple chrome metal, as thin as you can find, is good. It also adds a little "bling" to a rear end ensemble that, apart form the STS badge and the tailpipes, has none. This would help balance the large back-up lights as well.
There is some really sweet looking 2005 STS License frames on E-bay right none . They are all chrome with STS on the bottom of the frames and some come with the chrome screw caps . The buy now price was only $9.00 dollars plus $7.00 dollars for shipping . To me they looked great if you like the chrome look!