You know that particular comic was set at a work function, not a con right? But this one was so I guess I still count.

But to answer your question...I dunno. Good point. You have people like Randy Millholland who have the odd little con-comics separate to their non-journal-comic. And there's, say Fans which has fictional depictions of cons (as does SP, in it's way :))

Haha! I searched for "convention" on "Oh No Robot" and found This Real Life Strip. I love search engines.