It's a laser print on heavy satin card stock, matted to foam core raised off the wood with little bits of more foam core. The image is extracted from one of the official desktop wallpapers that are out there, it was the 1600x1200 version.
Thanks! For the little bulbous end of the trigger, I just stuck the end in a small silicon mold I had lying around (I think it may have been of a large bullet, but irrelevant) filled it with resin then shaped and sanded it down by hand. For the butt of the gun I used the nozzle's pre-existing pipe threading on the end to connect two steel pipe couplers to add some length, similar to this:
Then just roughed them up really well and then Bondo.