In memory of... who?

That's what I was wondering. Maybe the artist of this picture?

"Pool: In Memory Of" = Images dedicated to artists, voice actors, and directors who have passed away.
In this case here, the artist.

(BTW the link is broken - maybe a mod should fix that?)

That would mean this picture isn't dedicated to the artist, but that the pictures is instead drawn by a now deceased artist. The pool isn't meant for that but you can create an artist entry and add that the artist is deceased (I'd do it but I'm getting Failbooru).