I'm currently looking at lots of alternative approaches to the norm, and the cost of pickguard blanks has always bothered me!
This morning I went to the local plastics/perspex mob and I may have stumbled across an interesting one. They showed me a product called High Impact Polystyrene (HIPS). Despite my reservations about the fact it had the name polystyrene in it, it is effectively an easily fabricated plastic. It's available in .25 to 3mm thicknesses, and a 1370 x 760 sheet of white in 3mm is $50 (and I'm sure I can find cheaper). That should be enough for at least 8-10 pickguards. One drawback is that I can only find it in black or white (although it does seem other colours are possible to source), but I did ask the guy about how easy it is to glue two sheets together and he reckons there are a couple of spray adhesives that would work well. On that basis getting white/black/white 1mm sheets and gluing them together could be interesting.
I've subsequently read on other forums that it's very easy to work with too - sanding/cutting/routing etc.
I'll probably go ahead with making a couple in the next week or so and will report back, but for now just thought I'd share.