Has the artist given his permission for the work to be displayed outside of his site? If not, copyright is still his, and the image can't really be displayed on Wikipedia.
It's called fair use. While fair use is often abused around here, using a portion of a comic in an article discussing the comic in a non-commercial "educational" context is about as solid a fair use case as one can make. -- Cyrius|✎ 06:00, 26 July 2005 (UTC)