My attention was directed to this topic and I'm very much of a mixed mind on it. The intention of the Gallery when we set it up on the site was for members to share their personal pictures and artwork. That is, stuff they have firm copyright control on.
Because this is such a gray area on what is and is not public domain, we do not actively police this and expect our members to be doing what is right. Our posted Terms of Service cover this.
Now, as a writer myself, I also use pictures for the characters I write. I don't post these in public. I have had a talented artist render some of my characters and I have posted those with his permission though, for example.
Perhaps the safest solution for everyone is that we authors ask some of the artistically talented types on site to render characters for us in their medium of choice that we can then display? And if that's not available, link externally? This keeps everyone on Gay Authors, the site itself, free and clear of legal issues while addressing the very legitimate need of some authors to show images of what they have in mind.