I have seen a few scattered douga/genga from 
zoids... mostly of the main girl character from 
the original Zoids series.  The ones I saw (it's 
been several months now) were on YJ, and I found 
them under a general 'douga' search... 

I have yet to see any male characters, or any 
characters at all from Chaotic Century... which 
sucks, cuz there are a few guy characters that 
even I want. ^^;;

hope that helps, and good luck finding 
sketches...

Cheers!
~yaten