I've commissioned from three different artists, 
have talked to most others and been to their 
commercial websites, and I also paint fancels 
myself. And I can easily say that Lia from Baka 
Neko Fancels does the most incredible work I've 
ever come across! Her prices are the best, her 
quality and skill amazing, she has good work 
ethic (she'll never let you down) and she's the 
most friendly person you'll meet!! *^__^* 

Here's the fancel that I bought from her 
originally, Tsukasa from ".Hack:/SIGN". It was 
the first time I ever felt a "must have" impulse 
regarding any fanart! I love it! ^^;

Lia hasn't updated her site in awhile due to 
personal restraints, but I do think she's still 
answering email. Her site:
 
http://www.lvcm.com/genzou/

I don't know if she takes requests, but I also 
admire Clover's work:
http://www.citlink.net/~genrou/fancel1.htm

But I agree that you should shop around first, as 
everyone has their own opinions and tastes. 
Cels.org pretty much lists all the exisiting fan 
cel artists sites. And for more opinions from us 
lot, you could always use the search thingy at 
the bottom and type in "fan art" in the topic 
line, see all our past threads, positive and 
negative. 

I'd also recommend going to Requiem's site and 
looking around. She has a forum for fancel 
artists and you'll find folks posting their work 
to look at. 

Darksidemillenium.com Fancel Stuffs^^:
http://www.darksidemillenium.com/cels/

Fancel Forum:
http://pub36.bravenet.com/forum/show.php?
usernum=3087734918&cpv=1

Good luck!
~ Heather :)