Hi there,
Im a pretty seasoned veteran of selling artwork 
(or at least, trying to) at cons.  It's kind of a 
toss-up.  You really do have to "sell out" to the 
crowd.  I took some pieces to Akon and they 
hardly sold at all.  Only two made it to auction, 
and the best one, the one I worked soooo hard on 
didnt even make it, and it sold for 17$ :(  
People were really only buying certain 
things...the people who go to the art auctions 
are sort particular.  Hand done stuff is much 
more likely to sell than digital Ive been told, 
which is why I didnt make much. Also, cel work 
sells very well.  Gundam W is very popular, as is 
CCSakura, Utena, Sailor Moon of course, and 
Dragon Ball stuffs.  Slayers is also a timeless 
classic, so it sells well.  Also, alot counts for 
presentation.  Framed stuff, matted stuff always 
gets more attention :).  Anything you can do to 
dress up your art is good. 

Ergh, for some reason people think digital art is 
easy to do, therefor not worth as much.  But, I 
tell you what, I do almost nothing but digital 
art because I have a muscle disorder, and the 
traditional ways just kill me.  I can sit and 
tell you that it's JUST as painstaking and 
difficult to do.  The digital work never sells as 
well as hand done stuff at shows though, unless 
it's something outstanding, and/or really huge.  
And, cels ALWAYS sell well, so good luck!  I 
think your cel here will do just fine ~_^!