Free to read, free to edit, what do you mean? Oh.
Hey, fanart has no place in a wiki where we are supposed to document the manga and anime. Any picture we need, we pull from the source material, so it's true to the origin and not distorted by other artists. So, yes, we have little "value of art" as you so well put it, but it's for a good reason.
And also, I say this time and time again: democracy is not an excuse to do whatever you want. The rights of the invidual must be balanced against the rights of the state. We don't use fanart, we don't WANT fanart, and we don't want you to PUT fanart. But we let you edit the wiki and read it for free. I think the small limitation on not putting fanart is a fair trade for the right to edit and read this wiki.
Actually one of the best DC wikis on the net, if not THE best. Why else would it be ranked on top of Google search results? Obviously because Google search results rank sites on quality, and not because one site didn't let you do what you wanted because it'd be bad for the site.
Ooh, look, a bunch of smilies (frownies) that show your anger.