Don't use vinyl if your body has a nitro cellulose finish. It reacts with the finish and eats a big hole in the finish.
Was lacking a decent sig. Still is.
plywood is a cheap and quick option
if you have a broken/crappy acoustic, you could rip the top or back off and use that
sheet metal is useful for grounding and shielding

just have a look around during day-to-day stuff, the options are up to your imagination
Find a printing material supplier and look for litho plate.
Light gauge alloy with a satin finish can be cut with an etching blade on a flat surface
(workbench not kitchen table) ! decorate with letraset and lacquer (many coats)
Hard work but you can get something really amazing.
Adobe clay, recycled adult toys, food. Whatever gets the job done.
Bear in mind that pickguard material can effect the tone greatly. Slapping a big metal pickguard on a guitar gives it a far, far brighter tone; large wood pickguards tend to make the guitar sound suitably softer. Of course if the pickguard in question is only a tiny one then the difference isn't as great, but ven with something like a Les Paul Junior which has a relatively small pickguard that doesn't touch any of the other hardware or electronics, material still makes a noticable difference.

Consider the look you want then try to find a plastic/celluloid material that fits that, unless you're comfortable (or even want) the change in tone and resonance that particular materials bring. Standard plastic guards are most popular precisely because they don't particularly effect the tone of the instrument.
Yes, I know everything. No, I can't play worth a damn.
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