Sourcing fan art is fine as a gradual project, as it is wholly constructive.
Deleting fan art is fine as a gradual project as well and it is wholly constructive for the same reasons.
We could simply write in our rules that if somebody finds unsourced fan art in our profile pages, and know where it is from, they should add a credit to the artist, or ask content moderators or sysops for help if the pages are locked. That is not a big deal.
We could simply write in our rules that if someone finds fan art to just propose to remove it our thread made specifically for profile pictures, or ask a content moderator or sysop to remove it. It's not a big deal either.
Everything you mentioned here for sourcing fan art is the
exact same as removing fan art. With the exception that sourcing fan art is a lot more work as well as a legal risk.
Removing a massively large part of all images from our profile pages would be wholly massively aesthetically destructive for the wiki and as such a waste of time and resources that would be better spent elsewhere, gradual process or not.
It's not destructive at all, every single wiki out there doesn't use fan art and they're perfectly fine. Whether we have a pretty picture or not on our profiles will not effect our wiki's standings in the slightest. Removing fan art is as much of a "waste of time and resources" as sourcing is, except, again, sourcing is
much more work. With worse gain as it just makes our wiki look unprofessional and puts us at an unnecessary legal risk.
Also, I think that the legal risks are greatly exaggerated here. In the past 7 years, there has been only one instance that I know of where the artist wanted their images removed and deleted, and we instantly complied. That seems like the only thing that might happen.
You are also greatly exaggerating the impact removing fan art would have. You're acting as if removing fan art will collapse the wiki, or that we're forced to make it into such a great endeavour that we have to complete it in a few hours.
People don't come to a wiki called
Versus Battle Wiki to look at pretty pictures, they're here to debate whether their fictional character will beat another fictional character. I guarantee you that even if we removed every single picture on the wiki, the wiki won't drop more than a few percent. Stop making it out to be all doom and gloom to something that's an extremely minor aesthetic change.