Joel,

I think a multiple light setup might be more advantageous to making the guitars look their best. Maybe move the guitar away from the black background and then using rim lights for separation?

One major issue I see has to do with the post processing. Check out the very jagged (and partially missing) tuning knobs:
http://www.destroyallguitars.com/ima...Seafoam-05.jpg

It looks like the same problem extends to parts of the wood grain, too.

Sean