Here are mine from 2007. The theme was a slightly deranged hospital, performing "facial constructive surgery" on patients in a "persistent vegetative state" if you get my drift...
This was the mailing label that went on a 6x9 manila envelope:
This was the invitation text, describing the proceedings in pseudo-medical terms:
And an X-ray of an example "patient", printed on transparency sheets, just to help the atmosphere (and get the point across that it was a pumpkin carving party.):