How I see it is you can cosplay as whatever you want, I just highly recommend it not be racist, promote any type of hatred, and be courteous of people's religious views too. In my personal opinion, unless if it's done in humor, and I mean no offense to anyone, I prefer not to see an overweight man dressed as something like a Greco Roman wrestler or an overweight woman dressed as Rikku. I was once well overweight, so I honestly mean no offense, but I knew back then (and personally despite losing some weight still know) that I shouldn't be in too revealing of costumes.
If you think you can pull off a character properly or give a humorous take of a certain character, I see no harm in trying whatever you feel. One positive thing I can say about ACen and most other cons I have been to, most people don't come up to you and say "Your Costume sucks" or "You make a horrible (insert character)!" If they do, most people snicker from a distance. Either way, if you think it will be fun to do, just do it!
I'll admit, I always try to gain some attention with my characters, I think most of us do.
Forgot to mention, as far as someone of another race portraying a character that isn't their race, I don't think that's a problem at all. If anything, it makes me more interested in taking their picture.
This post has been edited by STVO: 14 June 2011 - 10:18 PM