You need:
- Web hosting with CGI/Perl support, so you have somewhere to store files, and to run the scripts that sit and wait for people to submit their pictures to.
- An oekaki package like
Shipainter.
... Except, I also haven't had any luck setting one up, otherwise InsanityManga.net and SMASH! would probably have Oekaki boards by now.

There appears to be something missing from the Shipainter package (getpic.cgi and friends), and the only results I find online are either unhelpful or downright antagonistic (I'm looking at you, /prog/ board).
So, uh... Good luck. D:
Edit: I found
this page that seems to indicate I should've downloaded a couple of other packages. Hope that helps.