Recently I went on a bender of reporting all of my artwork I could find on various RvB Facebook pages. A frustrating measure but nothing scares young people who don't know like official Facebook emails about copyright claims. I've done it on pintrest, tumblr, twitter, instagram...reposts are everywhere but unless we start sending the message that yes, one artist can take the time to report now and again, we'll never keep up.
Honestly it's why I took all my artwork down from here. All of my stolen art was from this site, likely because it's big and comes up in searches faster.
Remember, folks, reposting art isn't "honoring the artist" even if you source them 100% correctly. Without explicit permission, you are enjoying the fruits of labor you had no part in.
Artwork does not "belong to the fandom" as much as you'd like it to. The IP belongs to the company that owns it, and the artwork belongs to the artist.