Ken Anderson did a ton of loose character design sketches and background studies for The Rescuers. He was not concerned with the final look of the film, instead he presented valuable ideas which layout and background artists as well as the animators could put to good use. There is always a good dose of charm and personality in his work.
These drawings show how Ken staged the mice with objects from the human world in order to make them look small. Fun stuff!
See Milt Kahl's version of the following sketch here:
A couple of line ups showing the swamp folks.