Here's the full version of the image:
Invalid Link Removed
So as you can see, Luke looks to be a Telecaster kind of guy, Han is (unsurprisingly) rocking a V, Leia on lead vox, Chewie on drums, C3PO and R2R2 on keys...
And Darth Vader is the king of the show, laying down the low end with what appears to be a headless Steinberger.

(as a side note, I so want this poster on my wall)