Otakon has published on their site, not in their forums, the final official rules for artist's alley
I already read the relevant bits. Allow me to save you the trouble and tell you the important bits.
As I suggested they aren't going to allow you to sell what is essentially bootleg merchandise. So a Pikachu plushie is right out because a legitimate pikachu plushie is available.
They also wont allow t-shirts, buttons, pins or hats containing official character likenesses. That's something new. Allow me to quote them.Buttons, pins, hats, or t-shirts bearing official character likenesses.
Not allowed. These would be directly competing with stuff that is licensed and would definitely fall afoul of the owners. Clothing and accessories are usually licensed. (But if you're using characters you already own, or have explicit permission to use, you're fine.)
Tracings and slight modifications of existing licensed images are not allowed obviously.
And the final thing that is not allowed seems to be mass production. So making a zillion prints of your awesome Vash the Stampede drawing is a nono. Selling doujinshi is also ok, but if you have too many copies that's not good because you belong in the dealer's room.
I think the only rule that people will have a problem with here is the no buttons, t-shirts, pins and hats rule, and I kind of don't care. Mainly because it doesn't outlaw stickers, which I enjoy more. More stickers for me! Also, those are manufactured goods as opposed to crafted goods. It's obvious that they are saying that manufactured goods belong in the dealer's room and crafted goods belong in the alley, which I agree with.
Also, you might note that they aren't going to be giant assholes about this either. They'll let everyone set up their tables, and if they decide you are doing a nono they will give you a chance to just remove the offending items. That's good considering before the sentiment seemed to be that you wouldn't be allowed in at all before they inspected your wares.