Ernya seems to treat art requests well, or some anyway. there are a few that are always bringing in art and then a bunch that never get any even if they're a nice thread with good characters. I tried on Zantarni, but I've come to realize there are only two active threads in the art shops: mine which got revived when I went back to the site, and someone asking for art because they were leaving the site. I'll try kofk, but I have the equivalent of 15gold there.
people send art requests via DA sometimes. either rl payment or asking for freebies.