OK, I think I’ve extracted just about everything worth having from the various open art assets and open movie releases. Ryzom, Odd Job Jack, the several open Blender movies and Yo! Frankie game, etc, have all been pretty well trawled. This last free pack (at least, the last until someone makes another major open media production) is from the open movie Sita Sings the Blues. This is a wonderful feature-length animation from 2009 by Nina Paley.
I managed to extract 30 x 1920px backgrounds without characters in them, or else I Photoshopped out the characters, so you can use them with CrazyTalk Animator to make animations or comics. The original vector-art source files have not been released, so these are screen captures. Sita Sings the Blues is licensed under a Creative Commons Attribution ShareAlike license.
Download here (8Mb)
Installation: put these in a new ‘Sita’ sub-folder in C:\Users\Public\Documents\Reallusion\Custom\CrazyTalk Animator Custom\Background Ensure that all the thumbnail previews fully load before trying to drag a background to the Stage, or you will crash CTA.