Welcome to the insanity that is THORES(she not so secretly hates cosplayers as her designs attest).
As to a challenge....uhm...have you seen the TB artbook? The designs for Scissors Crown and all her other stuff? I don't think she's got a working definition for 'simple'.
As a larger person I think you can get away with most of the characters; though arguably, Aste, Shera and 'incognito Seth' might not do well. But that's just my opinion. But, if you want obscure, well, there's lots. Do you prefer human, methuselah, krusnik, vatican, rco or 'other'? You can always poke around in the TB photobucket account
(password THORES) and see what tickles your fancy.
~I've gone to look for myself, if I should return before I get back keep me here!~
Costume list 2009: Finished
17 initially planned :: 15 completed :: 6 moved to next year
Costume list 2010: Started
6 from '09 :: 9 initially planned, now up to 22 total