>>2615wpaint (the one you're using right now) is the only one that vichan comes with out-of-the-box support for. I agree that it's not very good :^p
tegaki (or plenty of other oekaki js apps, I'm sure) could be integrated, though it would take some work. currently, I'm looking into potentially migrating the site to a new, better imageboard software, so I'm trying to hold off on new features that are built on the vichan base. sorry (^^;)
but I can look into switching to a nicer oekaki applet on that software, if it's something people are interested in! :)