>>Is it one that are based on Wayne's plans?Not necessarily.
>>Is it some specific design philosphy that differs from others in some respect?
Yes, follow the link and down at the bottom of the page, Wayne has a white paper on the theory.
>>If I put together a speaker based on some of the stuff I read here, should I ask for a Pi decal to put on it?
I'll let the master tell ya.
>>What makes a "Pi-designed" speaker? What does this term mean?
See Wayne's white paper like I said above.