First suggestion: Do this contest again! One of the best (possibly THE best) contest I've seen. I'd been a lurker on this site for a long time, and I joined specifically to enter the contest. So Alyosha's remarks are very true - this contest worked to draw in a lot of new members.
It's these new members, in my opinion, who have to be considered in a contest like this. In our older contests, the results usually came back within a day, or certainly within the week. So if a new member joined with those expectations, he or she is expecting to at least hear something
pretty quickly. So for future contests, once the contest entry deadline is passed, I think it would be beneficial to toss up a note saying "Contest is now closed to new entries, and we're working on the judging." Since an estimation can be difficult to give accurately, let people know that you'll give an update in one week, two weeks, whatever, and then follow up. In two weeks, let them know you're still working on it and check back in two weeks. Exactly like Mark did with his entries. I think what was frustrating was the weeks of silence after Mark told us he had his entries completed.
That's my two cents. I get the feeling people are willing to wait for such a good thing, so long as they know what's going on