I guess I could upload the kra files (there are four of them since I made each panel separately, exported them to png and arranged them a fourth krita doc). Tho if I did that, would it even count as open source? A .kra file isn't really a source code, it's an archive that contains binaries.
Maybe licensing the art under some sort of Creative Commons Share alike license might serve your purpose? This being said I 100% get artists keeping full rights to their art. If you do that there is nothing wrong with that either.