I've just posted the first set of ItemRight-Music items to the HeroMachine 3 Alpha:
These are the ones I could "easily" convert from either HM2 or the Rock Star mini. And at that, they weren't all that easy, I had to do a lot of cutting and resizing and re-pasting/re-drawing.
I'm still working on the set, with all your suggestions in the last post still pending, but rather than make you wait for the complete release, I figured you might want to play with these as long as they were done. I tried to make the pattern-holding area fit on the face of the guitar, so with a little judicious sizing and moving, you can apply (for instance) the Union Jack flag from Insignia to the guitars.